Climate change feedback

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Climate_change_feedback

Some effects of global warming can either enhance (positive feedbacks) or inhibit (negative feedbacks) warming.

Climate change feedbacks are important in the understanding of global warming because feedback processes amplify or diminish the effect of each climate forcing, and so play an important part in determining the climate sensitivity and future climate state. Feedback in general is the process in which changing one quantity changes a second quantity, and the change in the second quantity in turn changes the first. Positive (or reinforcing) feedback amplifies the change in the first quantity while negative (or balancing) feedback reduces it.

The term "forcing" means a change which may "push" the climate system in the direction of warming or cooling. An example of a climate forcing is increased atmospheric concentrations of greenhouse gases. By definition, forcings are external to the climate system while feedbacks are internal; in essence, feedbacks represent the internal processes of the system. Some feedbacks may act in relative isolation to the rest of the climate system; others may be tightly coupled; hence it may be difficult to tell just how much a particular process contributes.

Forcings and feedbacks together determine how much and how fast the climate changes. The main positive feedback in global warming is the tendency of warming to increase the amount of water vapor in the atmosphere, which in turn leads to further warming. The main cooling response comes from the Stefan–Boltzmann law, the amount of heat radiated from the Earth into space changes with the fourth power of the temperature of Earth's surface and atmosphere. It is typically not considered a feedback. Observations and modelling studies indicate that there is a net positive feedback to warming. Large positive feedbacks can lead to tipping points—abrupt or irreversible changes in the climate system—depending upon the rate and magnitude of the climate change.

Positive

See also: Soil carbon feedback

Carbon cycle feedbacks

See also: Carbon cycle

There have been predictions, and some evidence, that global warming might cause loss of carbon from terrestrial ecosystems, leading to an increase of atmospheric CO₂ levels. Several climate models indicate that global warming through the 21st century could be accelerated by the response of the terrestrial carbon cycle to such warming. All 11 models in the C4MIP study found that a larger fraction of anthropogenic CO₂ will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO₂ varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The higher CO₂ levels led to an additional climate warming ranging between 0.1° and 1.5 °C. However, there was still a large uncertainty on the magnitude of these sensitivities. Eight models attributed most of the changes to the land, while three attributed it to the ocean. The strongest feedbacks in these cases are due to increased respiration of carbon from soils throughout the high latitude boreal forests of the Northern Hemisphere. One model in particular (HadCM3) indicates a secondary carbon cycle feedback due to the loss of much of the Amazon Rainforest in response to significantly reduced precipitation over tropical South America. While models disagree on the strength of any terrestrial carbon cycle feedback, they each suggest any such feedback would accelerate global warming.

Observations show that soils in the U.K have been losing carbon at the rate of four million tonnes a year for the past 25 years according to a paper in Nature by Bellamy et al. in September 2005, who note that these results are unlikely to be explained by land use changes. Results such as this rely on a dense sampling network and thus are not available on a global scale. Extrapolating to all of the United Kingdom, they estimate annual losses of 13 million tons per year. This is as much as the annual reductions in carbon dioxide emissions achieved by the UK under the Kyoto Treaty (12.7 million tons of carbon per year).

It has also been suggested (by Chris Freeman) that the release of dissolved organic carbon (DOC) from peat bogs into water courses (from which it would in turn enter the atmosphere) constitutes a positive feedback for global warming. The carbon currently stored in peatlands (390–455 gigatonnes, one-third of the total land-based carbon store) is over half the amount of carbon already in the atmosphere. DOC levels in water courses are observably rising; Freeman's hypothesis is that, not elevated temperatures, but elevated levels of atmospheric CO₂ are responsible, through stimulation of primary productivity.

Tree deaths are believed to be increasing as a result of climate change, which is a positive feedback effect.

Methane climate feedbacks in natural ecosystems.

Wetlands and freshwater ecosystems are predicted to be the largest potential contributor to a global methane climate feedback. Long-term warming changes the balance in the methane-related microbial community within freshwater ecosystems so they produce more methane while proportionately less is oxidised to carbon dioxide.

Arctic methane release

Photo shows what appears to be permafrost thaw ponds in Hudson Bay, Canada, near Greenland. (2008) Global warming will increase permafrost and peatland thaw, which can result in collapse of plateau surfaces.

 

Main article: Arctic methane release

Warming is also the triggering variable for the release of carbon (potentially as methane) in the arctic. Methane released from thawing permafrost such as the frozen peat bogs in Siberia, and from methane clathrate on the sea floor, creates a positive feedback. In April 2019, Turetsky et al. reported permafrost was thawing quicker than predicted. Recently the understanding of the climate feedback from permafrost improved, but potential emissions from the subsea permafrost remain unknown and are - like many other soil carbon feedbacks - still absent from most climate models.

Thawing permafrost peat bogs

See also: Arctic methane release and Permafrost carbon cycle

Western Siberia is the world's largest peat bog, a one million square kilometer region of permafrost peat bog that was formed 11,000 years ago at the end of the last ice age. The melting of its permafrost is likely to lead to the release, over decades, of large quantities of methane. As much as 70,000 million tonnes of methane, an extremely effective greenhouse gas, might be released over the next few decades, creating an additional source of greenhouse gas emissions. Similar melting has been observed in eastern Siberia. Lawrence et al. (2008) suggest that a rapid melting of Arctic sea ice may start a feedback loop that rapidly melts Arctic permafrost, triggering further warming. May 31, 2010. NASA published that globally "Greenhouse gases are escaping the permafrost and entering the atmosphere at an increasing rate - up to 50 billion tons each year of methane, for example - due to a global thawing trend. This is particularly troublesome because methane heats the atmosphere with 25 times the efficiency of carbon dioxide" (the equivalent of 1250 billion tons of CO₂ per year).

In 2019, a report called " Arctic report card " estimated the current greenhouse gas emissions from Arctic permafrost as almost equal to the emissions of Russia or Japan or less than 10% of the global emissions from fossil fuels.

The Sixth IPCC Assessment Report states that "projections from models of permafrost ecosystems suggest that future permafrost thaw will lead to some additional warming – enough to be important, but not enough to lead to a ‘runaway warming’ situation, where permafrost thaw leads to a dramatic, self-reinforcing acceleration of global warming."

Hydrates

Main article: Clathrate gun hypothesis

Methane clathrate, also called methane hydrate, is a form of water ice that contains a large amount of methane within its crystal structure. Extremely large deposits of methane clathrate have been found under sediments on the sea and ocean floors of Earth. The sudden release of large amounts of natural gas from methane clathrate deposits, in a runaway global warming event, has been hypothesized as a cause of past and possibly future climate changes. The release of this trapped methane is a potential major outcome of a rise in temperature; it is thought that this might increase the global temperature by an additional 5° in itself, as methane is much more powerful as a greenhouse gas than carbon dioxide. The theory also predicts this will greatly affect available oxygen content of the atmosphere. This theory has been proposed to explain the most severe mass extinction event on earth known as the Permian–Triassic extinction event, and also the Paleocene-Eocene Thermal Maximum climate change event. In 2008, a research expedition for the American Geophysical Union detected levels of methane up to 100 times above normal in the Siberian Arctic, likely being released by methane clathrates being released by holes in a frozen 'lid' of seabed permafrost, around the outfall of the Lena River and the area between the Laptev Sea and East Siberian Sea.

In 2020, the first leak of methane from the sea floor in Antarctica was discovered. The scientists are not sure what caused it. The area where it was found had not warmed yet significantly. It is on the side of a volcano, but it seems that it is not from there. The methane - eating microbes, eat the methane much fewer that was supposed, and the researchers think this should be included in climate models. They also claim that there is much more to discover about the issue in Antarctica. A quarter of all marine methane is found in the region of Antarctica

Abrupt increases in atmospheric methane

Literature assessments by the Intergovernmental Panel on Climate Change (IPCC) and the US Climate Change Science Program (CCSP) have considered the possibility of future projected climate change leading to a rapid increase in atmospheric methane. The IPCC Third Assessment Report, published in 2001, looked at possible rapid increases in methane due either to reductions in the atmospheric chemical sink or from the release of buried methane reservoirs. In both cases, it was judged that such a release would be "exceptionally unlikely" (less than a 1% chance, based on expert judgement). The CCSP assessment, published in 2008, concluded that an abrupt release of methane into the atmosphere appeared "very unlikely" (less than 10% probability, based on expert judgement). The CCSP assessment, however, noted that climate change would "very likely" (greater than 90% probability, based on expert judgement) accelerate the pace of persistent emissions from both hydrate sources and wetlands.

On 10 June 2019 Louise M. Farquharson and her team reported that their 12-year study into Canadian permafrost had "Observed maximum thaw depths at our sites are already exceeding those projected to occur by 2090. Between 1990 and 2016, an increase of up to 4 °C has been observed in terrestrial permafrost and this trend is expected to continue as Arctic mean annual air temperatures increase at a rate twice that of lower latitudes." Determining the extent of new thermokarst development is difficult, but there is little doubt the problem is widespread. Farquharson and her team guess that about 231,000 square miles (600,000 square kilometers) of permafrost, or about 5.5% of the zone that is permafrost year-round, is vulnerable to rapid surface thawing.

Decomposition

Main article: Decomposition

Organic matter stored in permafrost generates heat as it decomposes in response to the permafrost melting. As the tropics get wetter, as many climate models predict, soils are likely to experience greater rates of respiration and decomposition, limiting the carbon storage abilities of tropical soils.

Peat decomposition

Peat, occurring naturally in peat bogs, is a store of carbon significant on a global scale. When peat dries it decomposes, and may additionally burn. Water table adjustment due to global warming may cause significant excursions of carbon from peat bogs. This may be released as methane, which can exacerbate the feedback effect, due to its high global warming potential.

Rainforest drying

Rainforests, most notably tropical rainforests, are particularly vulnerable to global warming. There are a number of effects which may occur, but two are particularly concerning. Firstly, the drier vegetation may cause total collapse of the rainforest ecosystem. For example, the Amazon rainforest would tend to be replaced by caatinga ecosystems. Further, even tropical rainforests ecosystems which do not collapse entirely may lose significant proportions of their stored carbon as a result of drying, due to changes in vegetation.

Forest fires

See also: Climate change and ecosystems § Forests

The IPCC Fourth Assessment Report predicts that many mid-latitude regions, such as Mediterranean Europe, will experience decreased rainfall and an increased risk of drought, which in turn would allow forest fires to occur on larger scale, and more regularly. This releases more stored carbon into the atmosphere than the carbon cycle can naturally re-absorb, as well as reducing the overall forest area on the planet, creating a positive feedback loop. Part of that feedback loop is more rapid growth of replacement forests and a northward migration of forests as northern latitudes become more suitable climates for sustaining forests. There is a question of whether the burning of renewable fuels such as forests should be counted as contributing to global warming. Cook & Vizy also found that forest fires were likely in the Amazon Rainforest, eventually resulting in a transition to Caatinga vegetation in the Eastern Amazon region.

Desertification

Desertification is a consequence of global warming in some environments. Desert soils contain little humus, and support little vegetation. As a result, transition to desert ecosystems is typically associated with excursions of carbon.

Modelling results

The global warming projections contained in the IPCC's Fourth Assessment Report (AR4) include carbon cycle feedbacks. Authors of AR4, however, noted that scientific understanding of carbon cycle feedbacks was poor. Projections in AR4 were based on a range of greenhouse gas emissions scenarios, and suggested warming between the late 20th and late 21st century of 1.1 to 6.4 °C. This is the "likely" range (greater than 66% probability), based on the expert judgement of the IPCC's authors. Authors noted that the lower end of the "likely" range appeared to be better constrained than the upper end of the "likely" range, in part due to carbon cycle feedbacks. The American Meteorological Society has commented that more research is needed to model the effects of carbon cycle feedbacks in climate change projections.

Isaken et al. (2010) considered how future methane release from the Arctic might contribute to global warming. Their study suggested that if global methane emissions were to increase by a factor of 2.5 to 5.2 above (then) current emissions, the indirect contribution to radiative forcing would be about 250% and 400% respectively, of the forcing that can be directly attributed to methane. This amplification of methane warming is due to projected changes in atmospheric chemistry.

Schaefer et al. (2011) considered how carbon released from permafrost might contribute to global warming. Their study projected changes in permafrost based on a medium greenhouse gas emissions scenario (SRES A1B). According to the study, by 2200, the permafrost feedback might contribute 190 (+/- 64) gigatons of carbon cumulatively to the atmosphere. Schaefer et al. (2011) commented that this estimate may be low.

Implications for climate policy

Uncertainty over climate change feedbacks has implications for climate policy. For instance, uncertainty over carbon cycle feedbacks may affect targets for reducing greenhouse gas emissions. Emissions targets are often based on a target stabilization level of atmospheric greenhouse gas concentrations, or on a target for limiting global warming to a particular magnitude. Both of these targets (concentrations or temperatures) require an understanding of future changes in the carbon cycle. If models incorrectly project future changes in the carbon cycle, then concentration or temperature targets could be missed. For example, if models underestimate the amount of carbon released into the atmosphere due to positive feedbacks (e.g., due to melting permafrost), then they may also underestimate the extent of emissions reductions necessary to meet a concentration or temperature target.

Cloud feedback

Main article: Cloud feedback

Warming is expected to change the distribution and type of clouds. Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect; seen from above, clouds reflect sunlight and emit infrared radiation to space, and so exert a cooling effect. Whether the net effect is warming or cooling depends on details such as the type and altitude of the cloud. Low clouds tend to trap more heat at the surface and therefore have a positive feedback, while high clouds normally reflect more sunlight from the top so they have a negative feedback. These details were poorly observed before the advent of satellite data and are difficult to represent in climate models. Global climate models were showing a near-zero to moderately strong positive net cloud feedback, but the effective climate sensitivity has increased substantially in the latest generation of global climate models. Differences in the physical representation of clouds in models drive this enhanced climate sensitivity relative to the previous generation of models.

A 2019 simulation predicts that if greenhouse gases reach three times the current level of atmospheric carbon dioxide that stratocumulus clouds could abruptly disperse, contributing to additional global warming.

Gas release

Main article: Greenhouse gas

Release of gases of biological origin may be affected by global warming, but research into such effects is at an early stage. Some of these gases, such as nitrous oxide released from peat or thawing permafrost, directly affect climate. Others, such as dimethyl sulfide released from oceans, have indirect effects.

Ice–albedo feedback

Main articles: Arctic sea ice decline and Ice–albedo feedback

 

Aerial photograph showing a section of sea ice. The lighter blue areas are melt ponds and the darkest areas are open water; both have a lower albedo than the white sea ice. The melting ice contributes to ice–albedo feedback.

When ice melts, land or open water takes its place. Both land and open water are on average less reflective than ice and thus absorb more solar radiation. This causes more warming, which in turn causes more melting, and this cycle continues. During times of global cooling, additional ice increases the reflectivity, which reduces the absorption of solar radiation, resulting in more cooling through a continuing cycle. This is considered a faster feedback mechanism.

1870–2009 Northern hemisphere sea ice extent in million square kilometers. Blue shading indicates the pre-satellite era; data then is less reliable. In particular, the near-constant level extent in Autumn up to 1940 reflects lack of data rather than a real lack of variation.

Albedo change is also the main reason why IPCC predict polar temperatures in the northern hemisphere to rise up to twice as much as those of the rest of the world, in a process known as polar amplification. In September 2007, the Arctic sea ice area reached about half the size of the average summer minimum area between 1979 and 2000. Also in September 2007, Arctic sea ice retreated far enough for the Northwest Passage to become navigable to shipping for the first time in recorded history. The record losses of 2007 and 2008 may, however, be temporary. Mark Serreze of the US National Snow and Ice Data Center views 2030 as a "reasonable estimate" for when the summertime Arctic ice cap might be ice-free. The polar amplification of global warming is not predicted to occur in the southern hemisphere. The Antarctic sea ice reached its greatest extent on record since the beginning of observation in 1979, but the gain in ice in the south is exceeded by the loss in the north. The trend for global sea ice, northern hemisphere and southern hemisphere combined is clearly a decline.

Ice loss may have internal feedback processes, as melting of ice over land can cause eustatic sea level rise, potentially causing instability of ice shelves and inundating coastal ice masses, such as glacier tongues. Further, a potential feedback cycle exists due to earthquakes caused by isostatic rebound further destabilising ice shelves, glaciers and ice caps.

The ice–albedo in some sub-arctic forests is also changing, as stands of larch (which shed their needles in winter, allowing sunlight to reflect off the snow in spring and fall) are being replaced by spruce trees (which retain their dark needles all year).

Water vapor feedback

Main article: Water vapor feedback

If the atmospheres are warmed, the saturation vapor pressure increases, and the amount of water vapor in the atmosphere will tend to increase. Since water vapor is a greenhouse gas, the increase in water vapor content makes the atmosphere warm further; this warming causes the atmosphere to hold still more water vapor (a positive feedback), and so on until other processes stop the feedback loop. The result is a much larger greenhouse effect than that due to CO₂ alone. Although this feedback process causes an increase in the absolute moisture content of the air, the relative humidity stays nearly constant or even decreases slightly because the air is warmer. Climate models incorporate this feedback. Water vapor feedback is strongly positive, with most evidence supporting a magnitude of 1.5 to 2.0 W/m²/K, sufficient to roughly double the warming that would otherwise occur. Water vapor feedback is considered a faster feedback mechanism.

Ocean-warming feedback

According to the U.S. National Oceanic and Atmospheric Administration: Ocean warming provides a good example of a potential positive feedback mechanism. The oceans are an important sink for CO₂ through absorption of the gas into the water surface. As CO₂ increases, it increases the warming potential of the atmosphere. If air temperatures warm, it should warm the oceans. The ability of the ocean to remove CO₂ from the atmosphere decreases with increasing temperature. Because of this, increasing CO₂ in the atmosphere could have effects that actually intensify the increase in CO₂ in the atmosphere.

Negative

Blackbody radiation

As the temperature of a black body increases, the emission of infrared radiation back into space increases with the fourth power of its absolute temperature according to Stefan–Boltzmann law. This increases the amount of outgoing radiation as the Earth warms. It is called the Planck response, and sometimes considered a negative feedback (the Planck feedback).

Carbon cycle

Le Chatelier's principle

Following Le Chatelier's principle, the chemical equilibrium of the Earth's carbon cycle will shift in response to anthropogenic CO₂ emissions. The primary driver of this is the ocean, which absorbs anthropogenic CO₂ via the so-called solubility pump. At present this accounts for only about one third of the current emissions, but ultimately most (~75%) of the CO₂ emitted by human activities will dissolve in the ocean over a period of centuries: "A better approximation of the lifetime of fossil fuel CO₂ for public discussion might be 300 years, plus 25% that lasts forever". However, the rate at which the ocean will take it up in the future is less certain, and will be affected by stratification induced by warming and, potentially, changes in the ocean's thermohaline circulation.

Chemical weathering

Chemical weathering over the geological long term acts to remove CO₂ from the atmosphere. With current global warming, weathering is increasing, demonstrating significant feedbacks between climate and Earth surface. Biosequestration also captures and stores CO₂ by biological processes. The formation of shells by organisms in the ocean, over a very long time, removes CO₂ from the oceans. The complete conversion of CO₂ to limestone takes thousands to hundreds of thousands of years.

Net primary productivity

Net primary productivity changes in response to increased CO₂, as plants photosynthesis increased in response to increasing concentrations. However, this effect is swamped by other changes in the biosphere due to global warming.

The climate change-exacerbated 2019–2020 Australian wildfires caused oceanic deposition of wildfire aerosols, enhancing marine productivity and thereby caused widespread phytoplankton blooms. While these increased oceanic carbon dioxide uptake, the amount likely pales in comparison to the ~715 million tons of CO₂ the fires emitted and can contribute to ocean acidification which, in turn, may induce toxic algal blooms but is thought to generally closely follow future atmospheric CO₂ concentrations as climate change feedbacks on ocean pH approximately cancel.

Lapse rate

Main article: Lapse rate

The atmosphere's temperature decreases with height in the troposphere. Since emission of infrared radiation varies with temperature, longwave radiation escaping to space from the relatively cold upper atmosphere is less than that emitted toward the ground from the lower atmosphere. Thus, the strength of the greenhouse effect depends on the atmosphere's rate of temperature decrease with height. Both theory and climate models indicate that global warming will reduce the rate of temperature decrease with height, producing a negative lapse rate feedback that weakens the greenhouse effect. However, in regions with strong inversions, such as the polar regions, the lapse rate feedback can be positive because the surface warms faster than higher altitudes, resulting in inefficient longwave cooling. Measurements of the rate of temperature change with height are very sensitive to small errors in observations, making it difficult to establish whether the models agree with observations.

Impacts on humans

Feedback loops from the book Al Gore (2006). An inconvenient truth.

The primary human input to global climate change is increasing anthropogenic atmospheric carbon dioxide, which causes a complicated system of positive and negative drivers that ultimately—through such factors as heat stress, floods, droughts, and emerging diseases— have a negative effect on human population.

Classical economics

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Classical_economics 

Classical economics, classical political economy, or Smithian economics is a school of thought in political economy that flourished, primarily in Britain, in the late 18th and early-to-mid 19th century. Its main thinkers are held to be Adam Smith, Jean-Baptiste Say, David Ricardo, Thomas Robert Malthus, and John Stuart Mill. These economists produced a theory of market economies as largely self-regulating systems, governed by natural laws of production and exchange (famously captured by Adam Smith's metaphor of the invisible hand).

Adam Smith's The Wealth of Nations in 1776 is usually considered to mark the beginning of classical economics. The fundamental message in Smith's book was that the wealth of any nation was determined not by the gold in the monarch's coffers, but by its national income. This income was in turn based on the labor of its inhabitants, organized efficiently by the division of labour and the use of accumulated capital, which became one of classical economics' central concepts.

In terms of economic policy, the classical economists were pragmatic liberals, advocating the freedom of the market, though they saw a role for the state in providing for the common good. Smith acknowledged that there were areas where the market is not the best way to serve the common interest, and he took it as a given that the greater proportion of the costs supporting the common good should be borne by those best able to afford them. He warned repeatedly of the dangers of monopoly, and stressed the importance of competition. In terms of international trade, the classical economists were advocates of free trade, which distinguishes them from their mercantilist predecessors, who advocated protectionism.

The designation of Smith, Ricardo and some earlier economists as "classical" is due to a canonization which stems from Karl Marx's critique of political economy, where he critiqued those that he at least perceived as worthy of dealing with, as opposed to their "vulgar" successors. There is some debate about what is covered by the term classical economics, particularly when dealing with the period from 1830 to 1875, and how classical economics relates to neoclassical economics.

History

The classical economists produced their "magnificent dynamics" during a period in which capitalism was emerging from feudalism and in which the Industrial Revolution was leading to vast changes in society. These changes raised the question of how a society could be organized around a system in which every individual sought his or her own (monetary) gain. Classical political economy is popularly associated with the idea that free markets can regulate themselves.

Classical economists and their immediate predecessors reoriented economics away from an analysis of the ruler's personal interests to broader national interests. Adam Smith, following the physiocrat François Quesnay, identified the wealth of a nation with the yearly national income, instead of the king's treasury. Smith saw this income as produced by labour, land, and capital. With property rights to land and capital held by individuals, the national income is divided up between labourers, landlords, and capitalists in the form of wages, rent, and interest or profits. In his vision, productive labour was the true source of income, while capital was the main organizing force, boosting labour's productivity and inducing growth.

Ricardo and James Mill systematized Smith's theory. Their ideas became economic orthodoxy in the period ca. 1815–1848, after which an "anti-Ricardian reaction" took shape, especially on the European continent, that eventually became marginalist/neoclassical economics. The definitive split is typically placed somewhere in the 1870s, after which the torch of Ricardian economics was carried mainly by Marxian economics, while neoclassical economics became the new orthodoxy also in the English-speaking world.

Henry George is sometimes known as the last classical economist or as a bridge. The economist Mason Gaffney documented original sources that appear to confirm his thesis arguing that neoclassical economics arose as a concerted effort to suppress the ideas of classical economics and those of Henry George in particular.

Modern legacy

Classical economics and many of its ideas remain fundamental in economics, though the theory itself has yielded, since the 1870s, to neoclassical economics. Other ideas have either disappeared from neoclassical discourse or been replaced by Keynesian economics in the Keynesian Revolution and neoclassical synthesis. Some classical ideas are represented in various schools of heterodox economics, notably Georgism and Marxian economics – Marx and Henry George being contemporaries of classical economists – and Austrian economics, which split from neoclassical economics in the late 19th century. In the mid-20th century, a renewed interest in classical economics gave rise to the neo-Ricardian school and its offshoots.

Classical International Trade Economics

Adam Smith refuted Mercantilist thought with his most influential publication: An Inquiry into the Nature and Causes of the Wealth of Nations. He argued against mercantilism, and instead favored free trade and free markets, while believing that this would favor the countries who participate in free trade. He elucidated that mercantilist policies would benefit domestic producers but not the country because it prevents consumers buying products at competitive prices, therefore directing cashflow ineffectively. Smith believed that deviating from free trade costs society in a similar manner as to how monopolies negatively affect competition in a market.

During the classical era and after Adam Smith, David Ricardo became a prominent economist with thoughts on international trade. Ricardo’s most famous economic  theory was the theory of comparative advantage as the foundation of the international division of labor. He argued that international trade, in any case, would increase the standard of living. His main idea on international trade was that while it does add to real output produced in a country, the main benefits are derived from the encouragement of specialization and the division of labor on an international scale, leading to a more effective use of resources in all countries involved. One of Ricardo’s greatest assumptions and observations was that the factors of production are immobile between countries while finished goods are perfectly mobile, this assumption was critical to depict the advantages of international trade and specialization. His theory on international trade was weakened by how the labor theory of value clashes with the theory of comparative advantage. Ultimately both theories collide with a question on how the price is relatively determined and Ricardo simply stated that it does not hold in international trade theory.

John Stuart Mill would later come and solve this dilemma and further build upon Ricardo’s theory of comparative advantage. John Stuart Mill’s contribution to Ricardo’s theory of comparative advantage came about when he introduced demand to the equation. Mill introduced demand and was the first to promote the idea that demand and supply are functions of price, and the market equilibrium is where price is adjusted to where there is equilibrium between supply and demand. Overall, prior to Adam Smith and the classical economic wave, the main view of international trade was viewed negatively and not in favor of the countries who would participate in international trade with the economic policies of mercantilism. However, once Adam Smith, David Ricardo, and John Stuart Mill arrived with the classical wave of economics, international trade came to be viewed favorably and ultimately beneficial for all parties involved.

Classical theories of growth and development

Analyzing the growth in the wealth of nations and advocating policies to promote such growth was a major focus of most classical economists. However, John Stuart Mill believed that a future stationary state of a constant population size and a constant stock of capital was both inevitable, necessary and desirable for mankind to achieve. This is now known as a steady-state economy.

John Hicks & Samuel Hollander, Nicholas Kaldor, Luigi L. Pasinetti, and Paul A. Samuelson have presented formal models as part of their respective interpretations of classical political economy.

Value theory

Classical economists developed a theory of value, or price, to investigate economic dynamics. In political economics, value usually refers to the value of exchange, which is separate from the price. William Petty introduced a fundamental distinction between market price and natural price to facilitate the portrayal of regularities in prices. Market prices are jostled by many transient influences that are difficult to theorize about at any abstract level. Natural prices, according to Petty, Smith, and Ricardo, for example, capture systematic and persistent forces operating at a point in time. Market prices always tend toward natural prices in a process that Smith described as somewhat similar to gravitational attraction.

The theory of what determined natural prices varied within the Classical school. Petty tried to develop a par between land and labour and had what might be called a land-and-labour theory of value. Smith confined the labour theory of value to a mythical pre-capitalist past. Others may interpret Smith to have believed in value as derived from labour. He stated that natural prices were the sum of natural rates of wages, profits (including interest on capital and wages of superintendence) and rent. Ricardo also had what might be described as a cost of production theory of value. He criticized Smith for describing rent as price-determining, instead of price-determined, and saw the labour theory of value as a good approximation.

Some historians of economic thought, in particular, Sraffian economists, see the classical theory of prices as determined from three givens:

1. The level of outputs at the level of Smith's "effectual demand",
2. technology, and
3. wages.

From these givens, one can rigorously derive a theory of value. But neither Ricardo nor Marx, the most rigorous investigators of the theory of value during the Classical period, developed this theory fully. Those who reconstruct the theory of value in this manner see the determinants of natural prices as being explained by the Classical economists from within the theory of economics, albeit at a lower level of abstraction. For example, the theory of wages was closely connected to the theory of population. The Classical economists took the theory of the determinants of the level and growth of population as part of Political Economy. Since then, the theory of population has been seen as part of Demography. In contrast to the Classical theory, the following determinants of the neoclassical theory value are seen as exogenous to neoclassical economics:

1. tastes
2. technology, and
3. endowments.

Classical economics tended to stress the benefits of trade. Its theory of value was largely displaced by marginalist schools of thought which sees "use value" as deriving from the marginal utility that consumers finds in a good, and "exchange value" (i.e. natural price) as determined by the marginal opportunity- or disutility-cost of the inputs that make up the product. Ironically, considering the attachment of many classical economists to the free market, the largest school of economic thought that still adheres to classical form is the Marxian school.

Monetary theory

British classical economists in the 19th century had a well-developed controversy between the Banking and the Currency School. This parallels recent debates between proponents of the theory of endogeneous money, such as Nicholas Kaldor, and monetarists, such as Milton Friedman. Monetarists and members of the currency school argued that banks can and should control the supply of money. According to their theories, inflation is caused by banks issuing an excessive supply of money. According to proponents of the theory of endogenous money, the supply of money automatically adjusts to the demand, and banks can only control the terms and conditions (e.g., the rate of interest) on which loans are made.

Debates on the definition

The theory of value is currently a contested subject. One issue is whether classical economics is a forerunner of neoclassical economics or a school of thought that had a distinct theory of value, distribution, and growth.

The period 1830–75 is a timeframe of significant debate. Karl Marx originally coined the term "classical economics" to refer to Ricardian economics – the economics of David Ricardo and James Mill and their predecessors – but usage was subsequently extended to include the followers of Ricardo.

Sraffians, who emphasize the discontinuity thesis, see classical economics as extending from Petty's work in the 17th century to the break-up of the Ricardian system around 1830. The period between 1830 and the 1870s would then be dominated by "vulgar political economy", as Karl Marx characterized it. Sraffians argue that: the wages fund theory; Senior's abstinence theory of interest, which puts the return to capital on the same level as returns to land and labour; the explanation of equilibrium prices by well-behaved supply and demand functions; and Say's law, are not necessary or essential elements of the classical theory of value and distribution. Perhaps Schumpeter's view that John Stuart Mill put forth a half-way house between classical and neoclassical economics is consistent with this view.

Georgists and other modern classical economists and historians such as Michael Hudson argue that a major division between classical and neo-classical economics is the treatment or recognition of Economic rent. Most modern economists no longer recognize land/location as a factor of production, often claiming that rent is non-existent. Georgists and others argue that economic rent remains roughly a third of economic output.

Sraffians generally see Marx as having rediscovered and restated the logic of classical economics, albeit for his own purposes. Others, such as Schumpeter, think of Marx as a follower of Ricardo. Even Samuel Hollander has recently explained that there is a textual basis in the classical economists for Marx's reading, although he does argue that it is an extremely narrow set of texts.

Another position is that neoclassical economics is essentially continuous with classical economics. To scholars promoting this view, there is no hard and fast line between classical and neoclassical economics. There may be shifts of emphasis, such as between the long run and the short run and between supply and demand, but the neoclassical concepts are to be found confused or in embryo in classical economics. To these economists, there is only one theory of value and distribution. Alfred Marshall is a well-known promoter of this view. Samuel Hollander is probably its best current proponent.

Still another position sees two threads simultaneously being developed in classical economics. In this view, neoclassical economics is a development of certain exoteric (popular) views in Adam Smith. Ricardo was a sport, developing certain esoteric (known by only the select) views in Adam Smith. This view can be found in W. Stanley Jevons, who referred to Ricardo as something like "that able, but wrong-headed man" who put economics on the "wrong track". One can also find this view in Maurice Dobb's Theories of Value and Distribution Since Adam Smith: Ideology and Economic Theory (1973), as well as in Karl Marx's Theories of Surplus Value.

The above does not exhaust the possibilities. John Maynard Keynes thought of classical economics as starting with Ricardo and being ended by the publication of his own General Theory of Employment Interest and Money. The defining criterion of classical economics, on this view, is Say's law which is disputed by Keynesian economics. Keynes was aware, though, that his usage of the term 'classical' was non-standard.

One difficulty in these debates is that the participants are frequently arguing about whether there is a non-neoclassical theory that should be reconstructed and applied today to describe capitalist economies. Some, such as Terry Peach, see classical economics as of antiquarian interest.

Montessori education

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Montessori_education 

 

Traditional Montessori educational materials on display at the exhibition "Designed for children" at Triennale di Milano, Milan.

 

Children working with a moveable alphabet at a Montessori school

The Montessori method of education is a system of education for children that seeks to develop natural interests and activities rather than use formal teaching methods. A Montessori classroom places an emphasis on hands-on learning and developing real-world skills. It emphasizes independence and it views children as naturally eager for knowledge and capable of initiating learning in a sufficiently supportive and well-prepared learning environment. The underlying philosophy can be viewed as stemming from Unfoldment Theory. It discourages some conventional measures of achievement, such as grades and tests.

The method was developed in the early 20th century by Italian physician Maria Montessori, who developed her theories through scientific experimentation with her students; the method has since been used in many parts of the world, in public and private schools alike.

A range of practices exists under the name "Montessori", which is not trademarked. Popular elements include mixed-age classrooms, student freedom (including their choices of activity), long blocks of uninterrupted work time, specially trained teachers and prepared environment. Scientific studies regarding the Montessori method are mostly positive, with a 2017 review stating that "broad evidence" exists for its efficacy.

History

The Scarborough School at the Edward Harden Mansion in Sleepy Hollow, New York, listed on the National Register of Historic Places as the site of the first American Montessori school in 1911

Following her medical training, Maria Montessori began developing her educational philosophy and methods in 1897, attending courses in pedagogy at the University of Rome and learning educational theory. While visiting Rome's mental asylums during her schooling with a teacher, Montessori observed that confined children were in need of more stimulation from their environment. In 1907, she opened her first classroom, the Casa dei Bambini, or Children's House, in a tenement building in Rome. From the beginning, Montessori based her work on her observations of children and experimentation with the environment, materials, and lessons available to them. She frequently referred to her work as "scientific pedagogy".

In 1901, Maria Montessori met the prominent education reformers Alice and Leopoldo Franchetti. Maria Montessori was invited to hold her first course for teachers and to set up a "Casa dei Bambini" at Villa Montesca, the home of the Franchettis in Città di Castello. Montessori lived with the Franchettis for two years and refined her methodology together with Alice Franchetti. In 1909, she documented her theories in Il metodo della pedagogia scientifica (later translated into English as The Montessori Method in 1912). The Franchetti Barons financed the publication of the book, and the methodology had the name "Method Franchetti-Montessori".

Montessori education had spread to the United States by 1912 and became widely known in educational and popular publications. In 1913 Narcissa Cox Vanderlip and Frank A. Vanderlip founded the Scarborough School, the first Montessori school in the U.S. However, conflict arose between Montessori and the American educational establishment. The 1914 critical booklet The Montessori System Examined by influential education teacher William Heard Kilpatrick limited the spread of Montessori's ideas, and they languished after 1914. Montessori education returned to the United States in 1960 and has since spread to thousands of schools there. Montessori continued to extend her work during her lifetime, developing a comprehensive model of psychological development from birth to age 24, as well as educational approaches for children ages 0 to 3, 3 to 6, and 6 to 12.

Montessori education also spread throughout the world, including Southeast Asia and India, where Maria Montessori was interned during World War II. In October 1931, Indian independence leader Mahatma Gandhi met with Maria Montessori in London. At the time, Gandhi was very interested in the role the Montessori method might play in helping to build an independent nation. Thus, initially, Montessori education in India was connected to the Indian independence movement. Later, elite, private Montessori schools also arose, and in the 1950s, some Montessori schools opened to serve children from lower-socioeconomic families, a trend that continues today with foundation and government-funded schools.

Methods

A Montessori classroom in the United States

Montessori education is based on a model of human development. This educational style operates abiding by two beliefs: that psychological self-construction in children and developing adults occurs through environmental interactions and that children (especially under the age of six) have an innate path of psychological development. Based on her observations, Montessori believed that children who are at liberty to choose and act freely within an environment prepared according to her model would act spontaneously for optimal development.

Although a range of practices exists under the "Montessori" name, the Association Montessori Internationale (AMI) and the American Montessori Society (AMS) cite these elements as essential:

• Mixed-age classrooms: classrooms for children ages 2+1⁄2 or 3 to 6 years old are by far the most common, but 0–3, 6–9, 9–12, 12–15, and 15–18-year-old classrooms exist as well
• Student choice of activity from within a prescribed range of options
• Uninterrupted blocks of work time, ideally three hours long
• A constructivist or "discovery" model, in which students learn concepts from working with materials rather than by direct instruction
• Specialized educational materials are often made out of natural, aesthetic materials such as wood, rather than plastic
• A thoughtfully prepared environment where materials are organized by subject area, is accessible to children, and is appropriately sized
• Freedom, within limits
• A trained teacher experienced in observing a child's characteristics, tendencies, innate talents, and abilities

Montessori education involves free activity within a "prepared environment", meaning an educational environment tailored to basic human characteristics, to the specific characteristics of children at different ages, and to the individual personalities of each child. The function of the environment is to help and allow the child to develop independence in all areas according to his or her inner psychological directives. In addition to offering access to the Montessori materials appropriate to the age of the children, the environment should exhibit the following characteristics:

• An arrangement that facilitates movement and activity
• Beauty and harmony, cleanliness of environment
• Construction in proportion to the child and their needs
• Limitation of materials, so that only material that supports the child's development is included
• Order
• Nature in the classroom and outside of the classroom

Education practices

White Pine Montessori School in Moscow, Idaho, US

Infant and toddler programs

Montessori classrooms for children under three fall into several categories, with a number of terms being used. A nido, Italian for "nest", serves a small number of children from around two months to around 14 months, or when the child is confidently walking. A "Young Child Community" serves a larger number of children from around one year to 2+1⁄2 or 3 years old. Both environments emphasize materials and activities scaled to the children's size and abilities, opportunities to develop movement, and activities to develop independence. The development of independence in toileting is typically emphasized as well. Some schools also offer "Parent-Infant" classes, in which parents participate with their very young children.

Preschool and kindergarten

Hand painting in a Montessori school of Nigeria

Montessori classrooms for children from 2+1⁄2 or 3 to 6 years old are often called Children's Houses, after Montessori's first school, the Casa dei Bambini in Rome in 1906. A typical classroom serves 20 to 30 children in mixed-age groups, staffed by a fully trained lead teacher and assistants. Classrooms are usually outfitted with child-sized tables and chairs arranged singly or in small clusters, with classroom materials on child-height shelves throughout the room. Activities are for the most part initially presented by the teacher, after which they may be chosen more or less freely by the children as interest dictates. A teacher's role within a Montessori classroom is to guide and consult students individually by letting each child create their own learning pathway. Classroom materials usually include activities for engaging in practical skills such as pouring and spooning, washing up, scrubbing tables and sweeping. Also materials for the development of the senses, mathematical materials, language materials, music, art and cultural materials, including more science-based activities like 'sink and float', Magnetic and Non magnetic and candle and air.

Activities in Children's Houses are typically hands-on, tactile materials to teach concepts. For example, to teach writing, students use sandpaper letters. These are letters created by cutting letters out of sandpaper and placing them on wooden blocks. The children then trace these letters with their fingers to learn the shape and sound of each letter. Another example is the use of bead chains to teach math concepts, specifically multiplication. Specifically for multiples of 10, there is one bead that represents one unit, a bar of ten beads put together that represents 1×10, then a flat shape created by fitting 10 of the bars together to represent 10×10, and a cube created by fitting 10 of the flats together to represent 10×10×10. These materials help build a concrete understanding of basic concepts upon which much is built in the later years.

Elementary classrooms

Elementary school classrooms usually serve mixed-age 6- to 9-year-old and 9- to 12-year-old groupings; 6- to 12-year-old groups are also used. Lessons are typically presented to small groups of children, who are then free to follow up with independent work of their own as interest and personal responsibility dictate. Montessori educators give interdisciplinary lessons examining subjects ranging from biology and history to theology, which they refer to as "great lessons". These are typically given near the beginning of the school term and provide the basis for learning throughout the year. The great lessons offer inspiration and open doors to new areas of investigation.

Lessons include work in language, mathematics, history, the sciences, the arts, etc. Student-directed explorations of resources outside the classroom are integral to education. Montessori used the term "cosmic education" to indicate both the universal scope of lessons to be presented and the idea that education should help children realize the human role in the interdependent functioning of the universe.

Montessori schools are more flexible than traditional schools. In traditional schools, the students sit at tables or desks to do their work. At a Montessori school, the child gets to decide where they would like to work whether that is at a table or on the floor. It is about them going where they feel most comfortable. Anything a child would need during their learning experience is placed on a shelf that the student can easily get to. This promotes not only their learning, but also their independence because they do not need to ask for help as much. Montessori classrooms have an age range so that the younger students can look up to the older students and the older students can help the younger students as needed. It gives all age groups a chance to learn from one another. 

Middle and high school

Montessori education for this level is less developed than programs for younger children. Montessori did not establish a teacher training program or a detailed plan of education for adolescents during her lifetime. However, a number of schools have extended their programs for younger children to the middle school and high school levels. In addition, several Montessori organizations have developed teacher training or orientation courses and a loose consensus on the plan of study is emerging. Montessori wrote that "The essential reform of our plan from this point of view may be defined as follows: during the difficult time of adolescence it is helpful to leave the accustomed environment of the family in town and to go to quiet surroundings in the country, close to nature".

Digital technology

With the development of mobile touchscreen devices, some Montessori activities have been made into mobile apps. Mobile applications have been criticized due to the lack of physical interaction with objects.

Although not supported by all, most Montessori schools use digital technology with the purpose of preparing students for their future. Technology is not used the same as it would be used in a regular classroom, instead it is used "in meaningful ways". Students are not to simply replace "real-world activities with high-tech ones" such as the applications mentioned earlier.

Devices are not commonly used when students are being taught. When students have a question about something, they try to solve it themselves instead of turning to a device to try and figure out an answer.  When a device is used by a student, the teacher expects them to use it in a meaningful way. There has to be a specific purpose behind using technology. Before using a device, the student should ask themselves if using this device is the best way or if it is the only way to do a certain task. If the answer is yes to both of those questions, then that would be considered using technology in a meaningful way. 

Montessori's philosophy

Psychology

Montessori perceived specific elements of human psychology which her son and collaborator Mario Montessori identified as "human tendencies" in 1957. There is some debate about the exact list, but the following are clearly identified:

• Abstraction
• Activity
• Communication
• Exactness
• Exploration
• Manipulation (of the environment)
• Order
• Orientation
• Repetition
• Self-Perfection
• Work (also described as "purposeful activity")

"Planes" of development

Montessori observed four distinct periods, or "planes", in human development, extending from birth to 6 years, from 6 to 12, from 12 to 18, and from 18 to 24. She saw different characteristics, learning modes, and developmental imperatives active in each of these planes and called for educational approaches specific to each period.

The first plane extends from birth to around six years of age. During this period, Montessori observed that the child undergoes striking physical and psychological development. The first-plane child is seen as a concrete, sensorial explorer and learner engaged in the developmental work of psychological self-construction and building functional independence. Montessori introduced several concepts to explain this work, including the absorbent mind, sensitive periods, and normalization.

Educational materials like sandpaper letters are designed to appeal to young children's senses.

Montessori described the young child's behavior of effortlessly assimilating the sensorial stimuli of his or her environment, including information from the senses, language, culture, and the development of concepts with the term "absorbent mind". She believed that this is a power unique to the first plane, and that it fades as the child approached age six. Montessori also observed and discovered periods of special sensitivity to particular stimuli during this time which she called the "sensitive periods". In Montessori education, the classroom environment responds to these periods by making appropriate materials and activities available while the periods are active in each individual young child. She identified the following periods and their durations:

• Acquisition of language—from birth to around 6 years old
• Interest in small objects—from around 18 months to 3 years old
• Order—from around 1 to 3 years old
• Sensory refinement—from birth to around 4 years old
• Social behavior—from around 2+1⁄2 to 4 years old

Finally, Montessori observed in children from three to six years old a psychological state she termed "normalization". Normalization arises from concentration and focus on activity which serves the child's developmental needs, and is characterized by the ability to concentrate as well as "spontaneous discipline, continuous and happy work, social sentiments of help and sympathy for others."

The second plane of development extends from around six years to twelve years old. During this period, Montessori observed physical and psychological changes in children, and she developed a classroom environment, lessons, and materials, to respond to these new characteristics. Physically, she observed the loss of baby teeth and the lengthening of the legs and torso at the beginning of the plane, and a period of uniform growth following. Psychologically, she observed the "herd instinct", or the tendency to work and socialize in groups, as well as the powers of reason and imagination. Developmentally, she believed the work of the second-plane child is the formation of intellectual independence, of moral sense, and of social organization.

The third plane of development extends from around twelve years to around eighteen years of age, encompassing the period of adolescence. Montessori characterized the third plane by the physical changes of puberty and adolescence, but also psychological changes. She emphasized the psychological instability and difficulties in the concentration of this age, as well as the creative tendencies and the development of "a sense of justice and a sense of personal dignity." She used the term "valorization" to describe the adolescents' drive for an externally derived evaluation of their worth. Developmentally, Montessori believed that the work of the third plane child is the construction of the adult self in society.

The fourth plane of development extends from around eighteen years to around twenty-four years old. Montessori wrote comparatively little about this period and did not develop an educational program for the age. She envisioned young adults prepared by their experiences in Montessori education at the lower levels ready to fully embrace the study of culture and the sciences in order to influence and lead civilization. She believed that economic independence in the form of work for money was critical for this age, and felt that an arbitrary limit to the number of years in university-level study was unnecessary, as the study of culture could go on throughout a person's life.

Relationship to peace

Montessori believed that education had an important role in achieving world peace, stating in her 1936 book Education and Peace that "[p]reventing conflicts is the work of politics; establishing peace is the work of education." She felt that children allowed to develop according to their inner laws of development would give rise to a more peaceful and enduring civilization. From the 1930s to the end of her life, she gave a number of lectures and addresses on the subject.

Studies

A 2017 review on evaluations of Montessori education studies states that broad evidence exists that certain elements of the Montessori method (e.g., teaching early literacy through a phonics approach embedded in a rich language context, providing a sensorial foundation for mathematics education) are effective. At the same time, it was concluded that while some evidence exists that children may benefit cognitively and socially from Montessori education that sticks to original principles, it is less clear whether modern adapted forms of Montessori education are as effective. Lillard (2017) also reviews research on the outcomes of Montessori education.

A 1975 study published in Monographs of the Society for Research in Child Development showed that every year over a four-year period from Pre-K to Grade 2 children under a Montessori program had higher mean scores on the Stanford–Binet Intelligence Scales than those in DARCEE or traditional programs.

A 1981 study published in Young Children found that while Montessori programs could not be considered to have undergone detailed evaluation, they performed equal to or better than other programs in certain areas. A 2006 study published in Science magazine found that "when strictly implemented, Montessori education fosters social and academic skills that are equal or superior to those fostered by a pool of other types of schools." The study had a relatively small sample size and was severely criticized. Another study in the Milwaukee Public Schools found that children who had attended Montessori from ages 3–11 outperformed their high school classmates several years later on mathematics and science; another found that Montessori had some of the largest positive effects on the achievement of all programs evaluated.

Some studies have not found positive outcomes for children in Montessori classrooms. For example, a 2005 study in a Buffalo public Montessori magnet school "failed to support the hypothesis that enrollment in a Montessori school was associated with higher academic achievement." Explicitly comparing outcomes of Montessori classrooms in which children spent extra time with Montessori materials, a standard amount of time with the Montessori materials ('classic Montessori'), or no time at all with the materials (because they were in conventional classrooms), Lillard (2012) found the best outcomes for children in classic Montessori.

A 2017 study published by The Hechinger Report claims that despite financial background, students in Montessori schools did score higher on academic tests than their peers in the same economic classes who did not attend Montessori schools.

Trademark and branding

In 1967, the US Patent and Trademark Office ruled that "the term 'Montessori' has a generic and/or descriptive significance." According to many Montessori advocates, the lack of trademark protection has led to public misconceptions of the method due to some schools' using the term without adhering to Montessorian principles.

In the Philippines, the Department of Education (DepED) has noted the proliferation of private schools which misuse the term "Montessori" similar to how educational institutes present themselves as "international schools". As per Department of Education, Culture and Sports (DECS; now DepED) Order 65 issued in June 1997, the education department along with the Securities and Exchange Commission shall only allow schools to use the term 'Montessori', if they satisfy certain guidelines by the Federation of Philippine Montessori Schools.