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Sunday, November 10, 2019

Freeman Dyson

From Wikipedia, the free encyclopedia
 
Freeman Dyson


Freeman Dyson (2005).jpg
Born
Freeman John Dyson

15 December 1923 (age 95)
NationalityAmerican
Alma mater
Known for
Spouse(s)Verena Huber-Dyson (1950–1958)
Imme Jung (1958–)
ChildrenEsther Dyson, George Dyson, Dorothy Dyson, Mia Dyson, Rebecca Dyson, Emily Dyson
Awards
Scientific career
FieldsPhysics, mathematics
Institutions
Academic advisorsHans Bethe
InfluencesRichard Feynman
Abram Samoilovitch Besicovitch
Websitewww.sns.ias.edu/dyson
Notes
He is the son of George Dyson.

Freeman John Dyson FRS (born 15 December 1923) is an American theoretical physicist and mathematician, of British origin, known for his work in quantum electrodynamics, solid-state physics, astronomy and nuclear engineering. He is professor emeritus in the Institute for Advanced Study in Princeton, a member of the Board of Visitors of Ralston College and a member of the Board of Sponsors of the Bulletin of the Atomic Scientists.

Dyson originated several concepts that bear his name, such as Dyson's transform, a fundamental technique in additive number theory, which he developed as part of his proof of Mann's theorem; the Dyson tree, a hypothetical genetically-engineered plant capable of growing in a comet; the Dyson series, a perturbative series where each term is represented by Feynman diagrams; the Dyson sphere, a thought experiment that attempts to explain how a space-faring civilization would meet its energy requirements with a hypothetical megastructure that completely encompasses a star and captures a large percentage of its power output; and Dyson's eternal intelligence, a means by which an immortal society of intelligent beings in an open universe could escape the prospect of the heat death of the universe by extending subjective time to infinity while expending only a finite amount of energy. Dyson believes global warming is caused by increased carbon dioxide through burning fossil fuels, but is skeptical about the simulation models used to predict climate change, arguing that political efforts to reduce causes of climate change distract from other global problems that should take priority.

Biography

Early life

Born on 15 December 1923, at Crowthorne in Berkshire, England, Dyson is the son of the composer George Dyson, who was later knighted. His mother had a law degree, and after Dyson was born she worked as a social worker. Dyson had one sibling, his older sister, Alice, who remembered him as a boy surrounded by encyclopedias and always calculating on sheets of paper. At the age of four he tried to calculate the number of atoms in the sun. As a child, he showed an interest in large numbers and in the solar system, and was strongly influenced by the book Men of Mathematics by Eric Temple Bell. Politically, Dyson says he was "brought up as a socialist".

From 1936 to 1941 Dyson was a scholar at Winchester College, where his father was Director of Music. At age 17 he studied mathematics with G.H. Hardy at Trinity College, Cambridge (where he won a scholarship at age 15) and at age 19 was assigned to war work in the Operational Research Section (ORS) of the Royal Air Force's Bomber Command, where he developed analytical methods for calculating the ideal density for bomber formations to help the Royal Air Force bomb German targets during the Second World War. After the war, Dyson was readmitted to Trinity College, Cambridge, where he obtained a BA degree in mathematics. From 1946 to 1949 he was a Fellow of his college, occupying rooms just below those of the philosopher Ludwig Wittgenstein, who resigned his professorship in 1947. In 1947 Dyson published two papers in number theory. Friends and colleagues describe him as shy and self-effacing, with a contrarian streak that his friends find refreshing but his intellectual opponents find exasperating. "I have the sense that when consensus is forming like ice hardening on a lake, Dyson will do his best to chip at the ice", Steven Weinberg said of him. His friend the neurologist and author Oliver Sacks said: "A favourite word of Freeman's about doing science and being creative is the word 'subversive'. He feels it's rather important not only to be not orthodox, but to be subversive, and he's done that all his life."

Career in the United States

On G. I. Taylor's advice and recommendation, Dyson moved to the United States in 1947 as a Commonwealth Fellow to earn a physics doctorate with Hans Bethe at Cornell University (1947–48). There he made the acquaintance of Richard Feynman. The budding English physicist recognized the brilliance of the flamboyant American and worked with him. He then moved to the Institute for Advanced Study (1948–49), before returning to England (1949–51), where he was a research fellow at the University of Birmingham.

In 1949 Dyson demonstrated the equivalence of two formulations of quantum electrodynamics (QED): Richard Feynman's diagrams and the operator method developed by Julian Schwinger and Shin'ichirō Tomonaga. He was the first person after their creator to appreciate the power of Feynman diagrams and his paper written in 1948 and published in 1949 was the first to make use of them. He said in that paper that Feynman diagrams were not just a computational tool but a physical theory and developed rules for the diagrams that completely solved the renormalization problem. Dyson's paper and also his lectures presented Feynman's theories of QED in a form that other physicists could understand, facilitating the physics community's acceptance of Feynman's work. J. Robert Oppenheimer, in particular, was persuaded by Dyson that Feynman's new theory was as valid as Schwinger's and Tomonaga's. Oppenheimer rewarded Dyson with a lifetime appointment at the Institute for Advanced Study, "for proving me wrong", in Oppenheimer's words.

Also in 1949, in related work, Dyson invented the Dyson series. It was this paper that inspired John Ward to derive his celebrated Ward–Takahashi identity.

In 1951 Dyson joined the faculty at Cornell as a physics professor, though he still had no doctorate, and in 1953 he received a permanent post at the Institute for Advanced Study in Princeton, New Jersey, where he has remained. In 1957 he became a naturalized citizen of the United States and renounced his British nationality. One reason he gave decades later is that his children born in the United States had not been recognized as British subjects.

From 1957 to 1961 Dyson worked on Project Orion, which proposed the possibility of space-flight using nuclear pulse propulsion. A prototype was demonstrated using conventional explosives, but the 1963 Partial Test Ban Treaty, which Dyson was involved in and supported, permitted only underground nuclear weapons testing, so the project was abandoned.

In 1958 Dyson was a member of the design team under Edward Teller for TRIGA, a small, inherently safe nuclear reactor used throughout the world in hospitals and universities for the production of medical isotopes

A seminal paper by Dyson came in 1966, when, together with Andrew Lenard and independently of Elliott H. Lieb and Walter Thirring, he proved rigorously that the Pauli exclusion principle plays the main role in the stability of bulk matter. Hence it is not the electromagnetic repulsion between outer-shell orbital electrons that prevents two stacked wood blocks from coalescing into a single piece, but the exclusion principle applied to electrons and protons that generates the classical macroscopic normal force. In condensed matter physics, Dyson also analysed the phase transition of the Ising model in 1 dimension and spin waves.

Dyson also did work in a variety of topics in mathematics, such as topology, analysis, number theory and random matrices. In 1973 the number theorist Hugh Lowell Montgomery was visiting the Institute for Advanced Study and had just made his pair correlation conjecture concerning the distribution of the zeros of the Riemann zeta function. He showed his formula to the mathematician Atle Selberg, who said that it looked like something in mathematical physics and that Montgomery should show it to Dyson, which he did. Dyson recognized the formula as the pair correlation function of the Gaussian unitary ensemble, which physicists have studied extensively. This suggested that there might be an unexpected connection between the distribution of primes (2, 3, 5, 7, 11,  ...) and the energy levels in the nuclei of heavy elements such as uranium.

Around 1979 Dyson worked with the Institute for Energy Analysis on climate studies. This group, under Alvin Weinberg's direction, pioneered multidisciplinary climate studies, including a strong biology group. Also during the 1970s, Dyson worked on climate studies conducted by the JASON defense advisory group.

Dyson retired from the Institute for Advanced Study in 1994. In 1998 he joined the board of the Solar Electric Light Fund. As of 2003 he was president of the Space Studies Institute, the space research organization founded by Gerard K. O'Neill; as of 2013 he is on its board of trustees. Dyson is a longtime member of the JASON group. 

Dyson has won numerous scientific awards, but never a Nobel Prize. Nobel physics laureate Steven Weinberg has said that the Nobel committee has "fleeced" Dyson, but Dyson himself remarked in 2009, "I think it's almost true without exception if you want to win a Nobel Prize, you should have a long attention span, get hold of some deep and important problem and stay with it for ten years. That wasn't my style." Dyson is a regular contributor to The New York Review of Books.

In 2012 Dyson published (with William H. Press) a fundamental new result about the prisoner's dilemma in the Proceedings of the National Academy of Sciences of the United States of America.

Family

With his first wife, the Swiss mathematician Verena Huber-Dyson, Dyson had two children, Esther and George. In 1958 he married Imme Jung, a masters runner, and they had four more children, Dorothy, Mia, Rebecca, and Emily Dyson.

Dyson's eldest daughter, Esther, is a digital technology consultant and investor; she has been called "the most influential woman in all the computer world". His son, George, is a historian of science, one of whose books is Project Orion: The Atomic Spaceship 1957–1965.

Concepts

Biotechnology and genetic engineering

Dyson admits his record as a prophet is mixed, but thinks it is better to be wrong than vague, and that in meeting the world's material needs, technology must be beautiful and cheap.
My book The Sun, the Genome, and the Internet (1999) describes a vision of green technology enriching villages all over the world and halting the migration from villages to megacities. The three components of the vision are all essential: the sun to provide energy where it is needed, the genome to provide plants that can convert sunlight into chemical fuels cheaply and efficiently, the Internet to end the intellectual and economic isolation of rural populations. With all three components in place, every village in Africa could enjoy its fair share of the blessings of civilization.
Dyson has coined the term "green technologies", based on biology instead of physics or chemistry, to describe new species of microorganisms and plants designed to meet human needs. He argues that such technologies would be based on solar power rather than the fossil fuels whose use he sees as part of what he calls "gray technologies" of industry. He believes that genetically engineered crops, which he describes as green, can help end rural poverty, with a movement based in ethics to end the inequitable distribution of wealth on the planet.

The Origin of Life

Dyson favors the dual origin theory: that life first formed as cells, then enzymes, and finally, much later, genes. This was first propounded by the Russian Alexander Oparin. J. B. S. Haldane developed the same theory independently. In Dyson's version of the theory life evolved in two stages, widely separated in time. Because of the biochemistry he regards it as too unlikely that genes could have developed fully blown in one process. Current cells contain adenosine triphosphate or ATP and adenosine 5'-monophosphate or AMP, which greatly resemble each other but have completely different functions. ATP transports energy around the cell, and AMP is part of RNA and the genetic apparatus. Dyson proposes that in a primitive early cell containing ATP and AMP, RNA and replication were invented accidentally because of the similarity between AMP and RNA. He suggests that AMP was produced when ATP molecules lost two of their phosphate radicals, and then one cell somewhere performed Eigen's experiment and produced RNA.

There is no direct evidence for the dual origin theory, because once genes developed, they took over, obliterating all traces of the earlier forms of life. In the first origin, the cells were probably just drops of water held together by surface tension, teeming with enzymes and chemical reactions, and having a primitive kind of growth or replication. When the liquid drop became too big, it split into two drops. Many complex molecules formed in these "little city economies" and the probability that genes would eventually develop in them was much greater than in the prebiotic environment.

Artist's concept of Dyson rings, forming a stable Dyson swarm, or "Dyson sphere"

Dyson sphere

In 1960 Dyson wrote a short paper for the journal Science titled "Search for Artificial Stellar Sources of Infrared Radiation". In it he speculated that a technologically advanced extraterrestrial civilization might surround its native star with artificial structures to maximize the capture of the star's energy. Eventually the civilization would enclose the star, intercepting electromagnetic radiation with wavelengths from visible light downward and radiating waste heat outward as infrared radiation. One method of searching for extraterrestrial civilizations would be to look for large objects radiating in the infrared range of the electromagnetic spectrum.
One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which surrounds its parent star.
Dyson conceived that such structures would be clouds of asteroid-sized space habitats, though science fiction writers have preferred a solid structure: either way, such an artefact is often called a Dyson sphere, although Dyson used the term "shell". Dyson says that he used the term "artificial biosphere" in the article to mean a habitat, not a shape. The general concept of such an energy-transferring shell had been advanced decades earlier by author Olaf Stapledon in his 1937 novel Star Maker, a source Dyson has credited publicly.

Dyson tree

Dyson has also proposed the creation of a Dyson tree, a genetically engineered plant capable of growing on a comet. He suggested that comets could be engineered to contain hollow spaces filled with a breathable atmosphere, thus providing self-sustaining habitats for humanity in the outer Solar System.
Plants could grow greenhouses ... just as turtles grow shells and polar bears grow fur and polyps build coral reefs in tropical seas. These plants could keep warm by the light from a distant Sun and conserve the oxygen that they produce by photosynthesis. The greenhouse would consist of a thick skin providing thermal insulation, with small transparent windows to admit sunlight. Outside the skin would be an array of simple lenses, focusing sunlight through the windows into the interior ... Groups of greenhouses could grow together to form extended habitats for other species of plants and animals.

Space colonies

I've done some historical research on the costs of the Mayflower's voyage, and on the Mormons' emigration to Utah, and I think it's possible to go into space on a much smaller scale. A cost on the order of $40,000 per person [1978 dollars, $143,254 in 2013 dollars] would be the target to shoot for; in terms of real wages, that would make it comparable to the colonization of America. Unless it's brought down to that level it's not really interesting to me, because otherwise it would be a luxury that only governments could afford.
Dyson has been interested in space travel since he was a child, reading such science fiction classics as Olaf Stapledon's Star Maker. As a young man, he worked for General Atomics on the nuclear-powered Orion spacecraft. He hoped Project Orion would put men on Mars by 1965, Saturn by 1970. For a quarter-century Dyson has been unhappy about how the government conducts space travel:
The problem is, of course, that they can't afford to fail. The rules of the game are that you don't take a chance, because if you fail, then probably your whole program gets wiped out.
He still hopes for cheap space travel, but is resigned to waiting for private entrepreneurs to develop something new and inexpensive.
No law of physics or biology forbids cheap travel and settlement all over the solar system and beyond. But it is impossible to predict how long this will take. Predictions of the dates of future achievements are notoriously fallible. My guess is that the era of cheap unmanned missions will be the next fifty years, and the era of cheap manned missions will start sometime late in the twenty-first century.
Any affordable program of manned exploration must be centered in biology, and its time frame tied to the time frame of biotechnology; a hundred years, roughly the time it will take us to learn to grow warm-blooded plants, is probably reasonable.
Dyson also proposed the use of bioengineered space colonies to colonize the Kuiper Belt on the outer edge of our Solar System. He proposed that habitats could be grown from space hardened spores. The colonies could then be warmed by large reflector plant leaves that could focus the dim, distant sunlight back on the growing colony. This was illustrated by Pat Rawlings on the cover of the National Space Society's Ad Astra magazine.

Space exploration

A direct search for life in Europa's ocean would today be prohibitively expensive. Impacts on Europa give us an easier way to look for evidence of life there. Every time a major impact occurs on Europa, a vast quantity of water is splashed from the ocean into the space around Jupiter. Some of the water evaporates, and some condenses into snow. Creatures living in the water far enough from the impact have a chance of being splashed intact into space and quickly freeze-dried. Therefore, an easy way to look for evidence of life in Europa's ocean is to look for freeze-dried fish in the ring of space debris orbiting Jupiter.
Freeze-dried fish orbiting Jupiter is a fanciful notion, but nature in the biological realm has a tendency to be fanciful. Nature is usually more imaginative than we are. ... To have the best chance of success, we should keep our eyes open for all possibilities.

Dyson's eternal intelligence

Dyson proposed that an immortal group of intelligent beings could escape the prospect of heat death by extending time to infinity while expending only a finite amount of energy. This is also known as the Dyson scenario.

Dyson's transform

His concept "Dyson's transform" led to one of the most important lemmas of Olivier Ramaré's theorem: that every even integer can be written as a sum of no more than six primes.

Dyson series

The Dyson series, the formal solution of an explicitly time-dependent Schrödinger equation by iteration, and the corresponding Dyson time-ordering operator an entity of basic importance in the mathematical formulation of quantum mechanics, are also named after Dyson.

Freeman Dyson in 2007 at the Institute for Advanced Study

Quantum physics and prime numbers

Dyson and Hugh Montgomery discovered an intriguing connection between quantum physics and Montgomery's pair correlation conjecture about the zeros of the Zeta function. The primes 2, 3, 5, 7, 11, 13, 17, 19, ... are described by the Riemann Zeta function, and Dyson had previously developed a description of quantum physics based on m by m arrays of totally random numbers. Montgomery and Dyson discovered that the eigenvalues of these matrices are spaced apart in exactly the same manner as Montgomery conjectured for the nontrivial zeros of the Zeta function. Andrew Odlyzko has verified the conjecture on a computer, using his Odlyzko–Schönhage algorithm to calculate many zeros. Dyson recognized this connection because of a number-theory question Montgomery asked him. Dyson had published results in number theory in 1947, while a Fellow at Trinity College, Cambridge, and so was able to understand Montgomery's question. If Montgomery had not been visiting the Institute for Advanced Study that week, this connection might not have been discovered.

There are in nature one, two, and three dimensional quasicrystals. Mathematicians define a quasicrystal as a set of discrete points whose Fourier transform is also a set of discrete points. Odlyzko has done extensive computations of the Fourier transform of the nontrivial zeros of the Zeta function, and they seem to form a one-dimensional quasicrystal. This would in fact follow from the Riemann hypothesis.

Rank of a partition

The rank of a partition, shown as its Young diagram

In number theory and combinatorics rank of a partition of a positive integer is a certain integer associated with the partition. Dyson introduced the concept in a paper published in the journal Eureka. It was presented in the context of a study of certain congruence properties of the partition function discovered by the mathematician Srinivasa Ramanujan. A different concept, sharing the same name, is used in combinatorics, where the rank is taken to be the size of the Durfee square of the partition.

Crank of a partition

In number theory, the crank of a partition is a certain integer associated with the partition in number theory. Dyson first introduced the term without a definition in a 1944 paper in a journal published by the Mathematics Society of Cambridge University. He then gave a list of properties this yet-to-be-defined quantity should have. In 1988, George E. Andrews and Frank Garvan discovered a definition for the crank satisfying the properties Dyson had hypothesized.

Astrochicken

Astrochicken is the name given to a thought experiment Dyson expounded in his book Disturbing the Universe (1979). He contemplated how humanity could build a small, self-replicating automaton that could explore space more efficiently than a manned craft could. He attributed the general idea to John von Neumann, based on a lecture von Neumann gave in 1948 titled The General and Logical Theory of Automata. Dyson expanded on von Neumann's automata theories and added a biological component.

Projects Dyson collaborated on

Lumpers and splitters

John von Neumann

Dyson has suggested that philosophers can be broadly, if simplistically, divided into splitters and lumpers. These roughly correspond to materialists, who imagine the world divided into atoms, and Platonists, who regard it as made up of ideas.

Helios

Helios is a design for a spacecraft propulsion system in which small (0.1 kiloton) nuclear bombs would be detonated in a chamber roughly 30 feet (9.1 m) in diameter. Water would be injected into the chamber, superheated by the explosion and expelled for thrust. The Helios propulsion system was conceived originally by Dyson.

Views

Climate change

Dyson agrees that anthropogenic global warming exists and that one of its main causes is the increase of carbon dioxide in the atmosphere resulting from the burning of fossil fuels. He has said that in many ways increased atmospheric carbon dioxide is beneficial, and that it is increasing biological growth, agricultural yields and forests. He believes that existing simulation models of climate change fail to account for some important factors, and that the results thus contain too great a margin of error to reliably predict future trends.

Dyson's views on global warming have been criticized. Climate scientist James Hansen said that Dyson "doesn't know what he's talking about.... If he's going to wander into something with major consequences for humanity and other life on the planet, then he should first do his homework—which he obviously has not done on global warming." Dyson replied that "[m]y objections to the global warming propaganda are not so much over the technical facts, about which I do not know much, but it's rather against the way those people behave and the kind of intolerance to criticism that a lot of them have."

In 2008 Dyson endorsed the now common usage of "global warming" as synonymous with global anthropogenic climate change, but argued that political efforts to reduce the causes of climate change distract from other global problems that should take priority.

Since originally taking interest in climate studies in the 1970s, Dyson has suggested that carbon dioxide levels in the atmosphere could be controlled by planting fast-growing trees. He calculates that it would take a trillion trees to remove all carbon from the atmosphere. In a 2014 interview he said, "What I'm convinced of is that we don't understand climate ... It will take a lot of very hard work before that question is settled."

Dyson is a member of the academic advisory council of the Global Warming Policy Foundation, a climate sceptic think tank chaired by Nigel Lawson.

Warfare and weapons

At the British Bomber Command, Dyson and colleagues proposed removing two gun turrets from the RAF Lancaster bombers, to cut the catastrophic losses due to German fighters in the Battle of Berlin. A Lancaster without turrets could fly 50 mph (80 km/h) faster and be much more maneuverable.
All our advice to the commander in chief [went] through the chief of our section, who was a career civil servant. His guiding principle was to tell the commander in chief things that the commander in chief liked to hear ... To push the idea of ripping out gun turrets, against the official mythology of the gallant gunner defending his crew mates ... was not the kind of suggestion the commander in chief liked to hear.
On hearing the news of the bombing of Hiroshima:
I agreed emphatically with Henry Stimson. Once we had got ourselves into the business of bombing cities, we might as well do the job competently and get it over with. I felt better that morning than I had felt for years ... Those fellows who had built the atomic bombs obviously knew their stuff ... Later, much later, I would remember [the downside].
I am convinced that to avoid nuclear war it is not sufficient to be afraid of it. It is necessary to be afraid, but it is equally necessary to understand. And the first step in understanding is to recognize that the problem of nuclear war is basically not technical but human and historical. If we are to avoid destruction we must first of all understand the human and historical context out of which destruction arises.
In 1967, in his capacity as a military adviser, Dyson wrote an influential paper on the issue of possible US use of tactical nuclear weapons in the Vietnam War. When a general said in a meeting, "I think it might be a good idea to throw in a nuke now and then, just to keep the other side guessing ..." Dyson became alarmed and obtained permission to write a report on the pros and cons of using such weapons from a purely military point of view. (This report, Tactical Nuclear Weapons in Southeast Asia, published by the Institute for Defense Analyses, was obtained, with some redactions, by the Nautilus Institute for Security and Sustainability under the Freedom of Information act in 2002.) It was sufficiently objective that both sides in the debate based their arguments on it. Dyson says that the report showed that, even from a narrow military point of view, the US was better off not using nuclear weapons. Dyson stated on the Dick Cavett show that the use of nuclear weaponry was a bad idea for the US at the time because "our targets were large and theirs were small." (His unstated assumption was that the Soviets would respond by supplying tactical nukes to the other side.)

Dyson opposed the Vietnam War, the Gulf War and the invasion of Iraq. He supported Barack Obama in the 2008 US presidential election and The New York Times has described him as a political liberal. He was one of 29 leading US scientists who wrote Obama a strongly supportive letter about his administration's 2015 nuclear deal with Iran.

Science and religion

Dyson was raised in what he has described as a “watered-down Church of England Christianity”. He is a nondenominational Christian and has attended various churches, from Presbyterian to Roman Catholic. Regarding doctrinal or Christological issues, he has said, "I am neither a saint nor a theologian. To me, good works are more important than theology."
Science and religion are two windows that people look through, trying to understand the big universe outside, trying to understand why we are here. The two windows give different views, but they look out at the same universe. Both views are one-sided, neither is complete. Both leave out essential features of the real world. And both are worthy of respect.
Trouble arises when either science or religion claims universal jurisdiction, when either religious or scientific dogma claims to be infallible. Religious creationists and scientific materialists are equally dogmatic and insensitive. By their arrogance they bring both science and religion into disrepute. The media exaggerate their numbers and importance. The media rarely mention the fact that the great majority of religious people belong to moderate denominations that treat science with respect, or the fact that the great majority of scientists treat religion with respect so long as religion does not claim jurisdiction over scientific questions.
Dyson partially disagrees with the famous remark by his fellow physicist Steven Weinberg that "With or without religion, good people can behave well and bad people can do evil; but for good people to do evil—that takes religion."
Weinberg's statement is true as far as it goes, but it is not the whole truth. To make it the whole truth, we must add an additional clause: "And for bad people to do good things—that [also] takes religion." The main point of Christianity is that it is a religion for sinners. Jesus made that very clear. When the Pharisees asked his disciples, "Why eateth your Master with publicans and sinners?" he said, "I come to call not the righteous but sinners to repentance." Only a small fraction of sinners repent and do good things but only a small fraction of good people are led by their religion to do bad things.
While Dyson has called himself a Christian, he identifies himself as agnostic about some of the specifics of his faith. For example, in reviewing The God of Hope and the End of the World by John Polkinghorne, Dyson wrote:
I am myself a Christian, a member of a community that preserves an ancient heritage of great literature and great music, provides help and counsel to young and old when they are in trouble, educates children in moral responsibility, and worships God in its own fashion. But I find Polkinghorne's theology altogether too narrow for my taste. I have no use for a theology that claims to know the answers to deep questions but bases its arguments on the beliefs of a single tribe. I am a practicing Christian but not a believing Christian. To me, to worship God means to recognize that mind and intelligence are woven into the fabric of our universe in a way that altogether surpasses our comprehension.
In The God Delusion (2006), biologist Richard Dawkins criticized Dyson for accepting the religious Templeton Prize in 2000: "It would be taken as an endorsement of religion by one of the world's most distinguished physicists." In 2000 Dyson declared that he is a (non-denominational) Christian, and he has disagreed with Dawkins on several occasions, as when he criticized Dawkins' understanding of evolution.

Named after Dyson

Honors and awards

Works

Books

Articles

  • "Freeman Dyson: By the Book". Sunday Book Review. The New York Times (Interview). 18 April 2015. p. 8.
  • "Birds and Frogs" – Notices of the American Mathematical Society, 2009

Documentaries

Special Report on Global Warming of 1.5 °C

From Wikipedia, the free encyclopedia
 
Cover of the Special Report on Global Warming of 1.5 °C
 
The Special Report on Global Warming of 1.5 °C (SR15) was published by the Intergovernmental Panel on Climate Change (IPCC) on 8 October 2018. The report, approved in Incheon, South Korea, includes over 6,000 scientific references, and was prepared by 91 authors from 40 countries. In December 2015, the 2015 United Nations Climate Change Conference called for the report. The report was delivered at the United Nations' 48th session of the IPCC to "deliver the authoritative, scientific guide for governments" to deal with climate change.

Its key finding is that meeting a 1.5 °C (2.7 °F) target is possible but would require "deep emissions reductions" and "rapid, far-reaching and unprecedented changes in all aspects of society." Furthermore, the report finds that "limiting global warming to 1.5 °C compared with 2 °C would reduce challenging impacts on ecosystems, human health and well-being" and that a 2 °C temperature increase would exacerbate extreme weather, rising sea levels and diminishing Arctic sea ice, coral bleaching, and loss of ecosystems, among other impacts. SR15 also has modelling that shows that, for global warming to be limited to 1.5 °C, "Global net human-caused emissions of carbon dioxide (CO2) would need to fall by about 45 percent from 2010 levels by 2030, reaching 'net zero' around 2050." The reduction of emissions by 2030 and its associated changes and challenges, including rapid decarbonisation, was a key focus on much of the reporting which was repeated through the world.

Main statements

Global warming will likely rise to 1.5 °C above pre-industrial levels between 2030 and 2052 if warming continues to increase at the current rate. SR15 provides a summary of, on one hand, existing research on the impact that a warming of 1.5 °C (equivalent to 2.7 °F) would have on the planet, and on the other hand, the necessary steps to limit global warming.

Even assuming full implementation of conditional and unconditional Nationally Determined Contributions submitted by nations in the Paris Agreement, net emissions would increase compared to 2010, leading to a warming of about 3 °C by 2100, and more afterwards. In contrast, limiting warming below or close to 1.5 °C would require to decrease net emissions by around 45% by 2030 and reach net zero by 2050 (i.e. keeping total cumulative emissions within a carbon budget). Even just for limiting global warming to below 2 °C, CO2 emissions should decline by 25% by 2030 and by 100% by 2075.

Pathways (i.e. scenarios and portfolios of mitigation options) that would allow such reduction by 2050  describe a rapid transition towards producing electricity through lower-emission methods, and increasing use of electricity instead of other fuels in sectors such as transportation. On average, the pathways describing the proportion of primary energy produced by renewables as increasing to 60%, while the proportion produced by coal drops to 5% and oil to 13%. Most pathways describe a larger role for nuclear energy and carbon capture and storage, and less usage of natural gas. They also assume that other measures are simultaneously undertaken: e.g. non-CO2 emissions (such as methane, black carbon, nitrous oxide) are to be similarly reduced, energy demand is unchanged, reduced by even 30% or offsetted by an unprecedented scale of carbon dioxide removal methods yet to be developed, while new policies and research allows to improve efficiency in agriculture and industry.
Pathways limiting global warming to 1.5 °C with no or limited overshoot would require rapid and far-reaching transitions in energy, land, urban and infrastructure (including transport and buildings), and industrial systems. These systems transitions are unprecedented in terms of scale, but not necessarily in terms of speed, and imply deep emissions reductions in all sectors, a wide portfolio of mitigation options and a significant upscaling of investments in those options. The rates of system changes [...] have occurred in the past within specific sectors, technologies and spatial contexts, but there is no documented historic precedent for their scale. — IPCC, SR15 Summary for policymakers, p. 17

Impact of 1.5 °C or 2 °C warming

According to the report, with global warming of 1.5 °C there would be increased risks to "health, livelihoods, food security, water supply, human security, and economic growth." Impact vectors include reduction in crop yields and nutritional quality. Livestock are also affected with rising temperatures through "changes in feed quality, spread of diseases, and water resource availability." "Risks from some vector-borne diseases, such as malaria and dengue fever, are projected to increase."

"Limiting global warming to 1.5°C, compared with 2°C, could reduce the number of people both exposed to climate-related risks and susceptible to poverty by up to several hundred million by 2050." Climate-related risks associated with increasing global warming depend on geographic location, "levels of development and vulnerability", and the speed and reach of climate mitigation and climate adaptation practices. For example, "urban heat islands amplify the impacts of heatwaves in cities." In general, "countries in the tropics and Southern Hemisphere subtropics are projected to experience the largest impacts on economic growth."

Weather, sea level, ice

Many regions and seasons experience warming greater than the global annual average, e.g. "2–3 times higher in the Arctic. Warming is generally higher over land than over the ocean," and it correlates with temperature extremes (which are projected to warm up to twice more on land than the global mean surface temperature) as well as precipitation extremes (both heavy rain and droughts). The assessed levels of risk generally increased compared to the previous IPCC report.

The "global mean sea level is projected rise (relative to 1986-2005) by 0.26 to 0.77 m by 2100 for 1.5 °C global warming" and about 0.1 m more for 2 °C. A difference of 0.1 m may correspond to 10 million more or fewer people exposed to related risks. "Sea level rise will continue beyond 2100 even if global warming is limited to 1.5 °C. Around 1.5 °C to 2 °C of global warming," irreversible instabilities could be triggered in Antarctica and "Greenland ice sheet, resulting in multi-metre rise in sea level." "An ice-free Arctic summer is projected once per century" (per decade) for 1.5 °C (respectively 2 °C). "Limiting global warming to 1.5 °C rather than 2 °C is projected to prevent the thawing over centuries of a permafrost area in the range of 1.5 to 2.5 million km2."

Ecosystems

"A decrease in global annual catch for marine fisheries of about 1.5 or 3 million tonnes for 1.5 °C or 2 °C of global warming" is projected by one global fishery model cited in the report. Coral reefs are projected to decline by a further 70–90% at 1.5 °C, and even more than 99% at 2 °C. "Of 105,000 species studied, 18% of insects, 16% of plants and 8% of vertebrates fare projected to lose over half of their climatically determined geographic range for global warming of 2 °C."

Approximately "4% or 13% of the global terrestrial land area is projected to undergo a transformation of ecosystems from one type to another" at 1 °C or 2 °C, respectively. "High-latitude tundra and boreal forests are particularly at risk of climate change-induced degradation and loss, with woody shrubs already encroaching into the tundra and will proceed with further warming."

Limiting the temperature increase

Human activities (anthropogenic greenhouse gas emissions) have already contributed 0.8–1.2 °C (1.4–2.2 °F) of warming. Nevertheless, the gases which have been emitted so far are unlikely to cause global temperature to rise to 1.5 °C alone, meaning a global temperature rise to 1.5 °C above pre-industrial levels is avoidable, assuming net zero emissions are reached soon.

Carbon budget

Limiting global warming to 1.5 °C requires staying within a total carbon budget, i.e. limiting total cumulative emissions of CO2. In other words, if net anthropogenic CO2 emissions are kept above zero, a global warming of 1.5 °C and more will eventually be reached. 

The value of the total net anthropogenic CO2 budget since the pre-industrial era is not assessed in the report. Estimates of 400–800 GtCO2 (gigatonnes of CO2) for the remaining budget are given (580 GtCO2 and 420 GtCO2 for a 66% and 50% probability of limiting warming to 1.5 °C, using global mean surface air temperature (GSAT); or 770 and 570 GtCO2, for 50% and 66% probabilities, using global mean surface temperature (GMST)). This is about 300 GtCO2 more compared to a previous IPCC report, due to updated understanding and further advances in methods. 

Emissions around the time of the report were depleting this budget at 42±3 GtCO2 per year. Anthropogenic emissions from the pre-industrial period to the end of 2017 are estimated to have reduced the budget for 1.5 °C by approximately 2200±320 GtCO2.

The estimates for the budget come with significant uncertainties, associated with: climate response to CO2 and non-CO2 emissions (these contribute about ±400 GtCO2 in uncertainty), the level of historic warming (±250 GtCO2), potential additional carbon release from future permafrost thawing and methane release from wetlands (reducing the budget by up to 100 GtCO2 over the century), and the level of future non-CO2 mitigation (±400 GtCO2).

Necessary emission reductions

Current nationally stated mitigation ambitions, as submitted under the Paris Agreement, would lead to global greenhouse gas emissions of 52–58 GtCO2eq per year, by 2030. "Pathways reflecting these ambitions would not limit global warming to 1.5 °C, even if supplemented by very challenging increases in the scale and ambition of emissions reductions after 2030." Instead, they are "broadly consistent" with a warming of about 3 °C by 2100, and more afterwards. 

Limit global warming to 1.5 °C with no or limited overshoot would require reducing emissions to below 35 GtCO2eq per year in 2030, regardless of the modelling pathway chosen. Most fall within 25–30 GtCO2eq per yer, a 40–50% reduction from 2010 levels.

The report says that for limiting warming to below 1.5 C "global net human-caused emissions of CO2 would need to fall by about 45% from 2010 levels by 2030, reaching net zero around 2050." Even just for limiting global warming to below 2 °C, CO2 emissions should decline by 25% by 2030 and by 100% by 2070.

Non-CO2 emissions should decline in more or less similar ways. This involves deep reductions in emissions of methane and black carbon: at least 35% of both by 2050, relative to 2010, to limit warming near 1.5 °C. Such measures could be undertaken in the energy sector and by reducing nitrous oxide and methane from agriculture, methane from the waste sector, and some other sources of black carbon and hydrofluorocarbons.
On timescales longer than tens of years, it may still be necessary to sustain net negative CO2 emissions and/or further reduce non-CO2 radiative forcing, in order to prevent further warming (due to Earth system feedbacks), reverse ocean acidification, and minimise sea level rise.

Pathways to 1.5 °C

Various pathways are considered, describing scenarios for mitigation of global warming, including portfolios for energy supply and negative emission technologies (like afforestation or carbon dioxide removal).

Examples of actions consistent with the 1.5 °C pathway include "shifting to low- or zero-emission power generation, such as renewables; changing food systems, such as diet changes away from land-intensive animal products; electrifying transport and developing 'green infrastructure', such as building green roofs, or improving energy efficiency by smart urban planning, which will change the layout of many cities." As another example, an increase of forestation by 10,000,000 square kilometres (3,900,000 sq mi) by 2050 relative to 2010 would be required.

The pathways also assume an increase in annual investments in low-carbon energy technologies and energy efficiency by roughly a factor of four to ten by 2050 compared to 2015.

Model pathways with no or limited overshoot of 1.5 °C
P1 P2 P3 P4
A scenario with low energy demand (LED) S1, based on SSP1 S2, based on SSP2 S5, based on SSP5
Grubler et al., 2018 Shared Socio-Economic Pathway 1 (SSP1: Sustainable development) Shared Socio-Economic Pathway 2 (SSP2: Middle of the road) Shared Socio-Economic Pathway 5 (SSP5: Fossil-fuelled development)

Negative emission technologies and geoengineering

The emission pathways that reach 1.5 °C contained in the report assume the use of negative emission technology to offset for remaining emissions. Pathways that overshoot the goal rely on them to exceed remaining emissions in order to return to 1.5 °C. However, understanding is still limited about the effectiveness of net negative emissions to reduce temperatures after an overshoot. Reversing an overshoot of 0.2 °C might not be achievable given considerable implementation challenges.

There are two main groups of geoengineering types in the report, carbon dioxide removal (CDR) and solar radiation management (SRM). For CDR the report highlights bioenergy with carbon capture and storage (BECCS). The report notes that apart from afforestation/reforestation and ecosystem restoration, "the feasibility of massive-scale deployment of many CDR technologies remains an open question", with areas of uncertainty regarding technology upscaling, governance, ethical issues, policy and carbon cycle. The report notes that CDR technology is in its infancy and the feasibility is an open question. Estimates from recent literature are cited, giving a potential of up to 5 GtCO2 per year for BECCS and up to 3.6 GtCO2 per year for afforestation. An analysis of the geoengineering proposals published in Nature Communication confirmed findings of the SR15, stating that "all are in early stages of development, involve substantial uncertainties and risks, and raise ethical and governance dilemmas. Based on present knowledge, climate geoengineering techniques cannot be relied on to significantly contribute to meeting the Paris Agreement temperature goals".

As for SRM, the report focuses on stratospheric aerosol injection, as it has the most available literature; however it is still an experimental technology. SRMs also "face large uncertainties and knowledge gaps as well as substantial risks, [...] and constraints"; "the impacts of SRM (both biophysical and societal), costs, technical feasibility, governance and ethical issues associated need to be carefully considered."

Process

There are three IPCC working groups: Working Group I (WG I), co-chaired by Valerie Masson-Delmotte and Panmao Zhai, covers the physical science of climate change. Working Group II (WG II), co-chaired by Hans-Otto Pörtner and Debra Roberts, examines "impacts, adaptation and vulnerability". The "mitigation of climate change" is dealt with by Working Group III (WG III), co-chaired by Priyardarshi Shukla and Jim Skea. The "Task Force on National Greenhouse Gas Inventories" "develops methodologies for measuring emissions and removals". There are also Technical Support Units that guide "the production of IPCC assessment reports and other products".

Contributors

Researchers from 40 countries, representing 91 authors and editors contributed to the report, which includes over 6,000 scientific references.

Reactions

Researchers

In his 1 October 2018 opening statement at the 48th Session held in Incheon, Korea, Hoesung Lee, who has been Chair of the IPCC since 6 October 2015, described this IPCC meeting as "one of the most important" in its history. Debra Roberts, IPCC contributor called it the "largest clarion bell from the science community". Roberts hopes "it mobilises people and dents the mood of complacency."

In a CBC interview, Paul Romer was asked if the Nobel Prize in economic sciences that he and William Nordhaus received shortly before the SR15 was released, was timed as a message. Romer said that he was optimistic that measures will be taken in time to avert climate catastrophe. Romer compared the angst and lack of political will in imposing a carbon tax to the initial angst surrounding the chlorofluorocarbon (CFC) ban and the positive impact it had on restoring the depleted ozone layer. In giving the Nobel to Nordhaus and Romer, the Royal Swedish Academy of Sciences cited Nordhaus as saying "the most efficient remedy for problems caused by greenhouse gases is a global scheme of universally imposed carbon taxes".

Howard J. Herzog, a senior research engineer at the Massachusetts Institute of Technology, said that carbon capture and storage technologies, except reforestation, are problematic because of their impact on the environment, health and high cost. In the article there is a link to another article that refers to a study published in the scientific journal "Nature Energy". The study says that we can limit warming to 1.5 degrees without carbon capture and storage, by technological innovation and changing lifestyle.

Politics

Australia

Prime Minister Scott Morrison emphasised that the report was not specifically for Australia but for the whole world. Energy Minister Angus Taylor said the Government would "not be distracted" by the IPCC report saying "A debate about climate change and generation technologies in 2050 won't bring down current power prices for Australian households and small businesses." Environment Minister Melissa Price said that scientists are "drawing a very long bow" to say coal should be phased out by 2050 and supported new coal-fired power stations pledging not to legislate the Paris targets. Australia is not on track to meet the commitments under Paris agreement according to modelling conducted by ClimateWorks Australia.

Canada

Canadian Environment Minister Catherine McKenna acknowledged that the SR15 report would say Canada is not "on track" for 1.5 °C. Canada will not be implementing new plans but it will continue to move forward on a "national price on carbon, eliminating coal-fired power plants, making homes and businesses more energy-efficient, and investing in clean technologies and renewable energy". In response to a question on the sense of urgency of the SR15 report during a 9 October interview on CBC News's Power and Politics Andrew Scheer, the Leader of the Opposition, promised that they are putting forward a "comprehensive plan to reduce CO2 without imposing a carbon tax" which Scheer said "raised costs without actually reducing emissions."

European Union

According to The New York Times, the European Union indicated it might add more ambitious reform goals centered around reducing emissions. On 9 October, the Council of the European Union presented their response to SR15 and their position for the Katowice Climate Change Conference of the Parties (COP 24) held in Poland in December 2018. Their environment ministers noted recent progress in legislation to reduce greenhouse gas emissions.

India

The Centre for Science and Environment said the repercussions for developing countries such as India, would be "catastrophic" at 2 °C warming and that the impact even at 1.5 °C described in SR15 is much greater than anticipated. Crop yields would decline and poverty would increase.

New Zealand

The Minister for Climate Change James Shaw said that the Report "has laid out a strong case for countries to make every effort to limit temperature rise to 1.5° Celsius above pre-industrial levels. ... The good news is that the IPCC's report is broadly in line with this Government's direction on climate change and it's highly relevant to the work we are doing with the Zero Carbon Bill."

United States

President Donald Trump said that he had received the report, but wanted to learn more about those who "drew it" before offering conclusions. In an interview with ABC's "This Week" the director of the National Economic Council, Larry Kudlow, stated, "personally, I think the UN study is way too difficult," and that the authors "overestimate" the likelihood for environmental disasters. Since the publication Trump stated in an interview on 60 Minutes that he didn't know that climate change is manmade and that "it'll change back again", the scientists who say it's worse than ever have "a very big political agenda" and that "we have scientists that disagree with [manmade climate change]."

COP24

The governments of four countries (the gas/oil-producers USA, Russia, Saudi Arabia and Kuwait) blocked a proposal to welcome the Intergovernmental Panel on Climate Change's (IPCC) Special Report on Global Warming of 1.5 °C at the 2018 United Nations Climate Change Conference (COP24).

IPCC Fifth Assessment Report

From Wikipedia, the free encyclopedia
 
Global Emissions by Economic Sector
 
The Fifth Assessment Report (AR5) of the United Nations Intergovernmental Panel on Climate Change (IPCC) is the fifth in a series of such reports. The IPCC was established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess scientific, technical and socio-economic information concerning climate change, its potential effects and options for adaptation and mitigation. 

The Fifth Assessment Report was finalized in 2014. As had been the case in the past, the outline of the AR5 was developed through a scoping process which involved climate change experts from all relevant disciplines and users of IPCC reports, in particular representatives from governments. Governments and organizations involved in the Fourth Report were asked to submit comments and observations in writing with the submissions analysed by the panel. The report was delivered in stages, starting with Working Group I's report on the physical science basis, based on 9,200 peer-reviewed studies. The summaries for policy makers were released on 27 September 2013 for the first report, on 31 March 2014 for the second report entitled "Impacts, Adaptation, and Vulnerability", and on 14 April 2014 for the third report entitled "Mitigation of Climate Change". The Synthesis Report was released on 2 November 2014, in time to pave the way for negotiations on reducing carbon emissions at the UN Climate Change Conference in Paris during late 2015.

Current status

The Fifth Assessment Report (AR5) consists of three Working Group (WG) Reports and a Synthesis Report. The first Working Group Report was published in 2013 and the rest were completed in 2014.
  • WG I: The Physical Science Basis – 30 September 2013, Summary for Policymakers published 27 September 2013.
  • WG II: Impacts, Adaptation and Vulnerability – 31 March 2014
  • WG III: Mitigation of Climate Change – 15 April 2014
  • AR5 Synthesis Report (SYR) – 2 November 2014
The AR5 provides an update of knowledge on the scientific, technical and socio-economic aspects of climate change

More than 800 authors, selected from around 3,000 nominations, were involved in writing the report. Lead authors' meetings and a number of workshops and expert meetings, in support of the assessment process, were held. A schedule of AR5 related meetings, review periods, and other important dates was published.

On 14 December 2012, drafts of the Working Group 1 (WG1) report were leaked and posted on the Internet. The release of the summary for policymakers occurred on 27 September 2013. Halldór Thorgeirsson, a UN official, warned that, because big companies are known to fund the undermining of climate science, scientists should be prepared for an increase in negative publicity at the time. "Vested interests are paying for the discrediting of scientists all the time. We need to be ready for that," he said.

Marking the finalization of the Physical Science Basis UN Secretary General Ban Ki-moon addressed the IPCC at Stockholm on 27 September 2013. He stated that "the heat is on. We must act". Jennifer Morgan, from the World Resources Institute, said "Hopefully the IPCC will inspire leadership, from the Mom to the business leader, to the mayor to the head of state." US Secretary of State John Kerry responded to the report saying "This is yet another wakeup call: those who deny the science or choose excuses over action are playing with fire."

Authors and editors

In March 2010, the IPCC received approximately 3,000 author nominations from experts around the world. At the bureau session held in Geneva, 19–20 May 2010, the three working groups presented their selected authors and review editors for the AR5. Each of the selected scientists, specialists and experts was nominated in accordance with IPCC procedures, by respective national IPCC focal-points, by approved observer organizations, or by the bureau. The IPCC received 50% more nominations of experts to participate in AR5 than it did for AR4. A total of 559 authors and review editors had been selected for AR4 from 2,000 proposed nominees. On 23 June 2010 the IPCC announced the release of the final list of selected coordinating lead authors, comprising 831 experts who were drawn from fields including meteorology, physics, oceanography, statistics, engineering, ecology, social sciences and economics. In comparison to the Fourth Assessment Report (AR4), participation from developing countries was increased, reflecting the ongoing efforts to improve regional coverage in the AR5. About 30% of authors came from developing countries or economies in transition. More than 60% of the experts chosen were new to the IPCC process, bringing fresh knowledge and perspectives.

Climate change 2013: report overview

On 23 June 2010, the IPCC announced the release of the final list of selected coordinating lead authors, comprising 831 experts. The working group reports would be published during 2013 and 2014. These experts would also provide contributions to the Synthesis Report published in late 2014.

The Fifth Assessment Report (Climate Change 2013) would be released in four distinct sections:
  • Working Group I Report (WGI): Focusing on the physical science basis and including 258 experts.
  • Working Group II Report (WGII): Assessing the impacts, adaptation strategies and vulnerability related to climate change and involving 302 experts.
  • Working Group III Report (WGIII): Covering mitigation response strategies in an integrated risk and uncertainty framework and its assessments carried out by 271 experts.
  • The Synthesis Report (SYR): Final summary and overview.

Working group I contribution

The full text of Climate Change 2013: The Physical Science Basis was released in an unedited form on Monday, 30 September 2013. It was over 2,000 pages long and cited 9,200 scientific publications. The full, edited report was released online in January 2014 and published in physical form by Cambridge University Press later in the year.

Summary for Policymakers

A concise overview of Working Group I's findings was published as the Summary for Policymakers on 27 September 2013. The level of confidence in each finding was rated on a confidence scale, qualitatively from very low to very high and, where possible, quantitatively from exceptionally unlikely to virtually certain (determined based on statistical analysis and expert judgement).

Likelihood scale used in the report
Term Likelihood of the outcome
Virtually certain 99–100 % probability
Extremely likely 95–100 % probability
Very likely 90–100 % probability
Likely 66–100 % probability
More likely than not 50–100 % probability
About as likely as not 33 to 66% probability
Unlikely 0–33 % probability
Very unlikely 0–10 % probability
Extremely unlikely 0–5 % probability
Exceptionally unlikely 0–1 % probability

The principal findings were:
General
  • Warming of the atmosphere and ocean system is unequivocal. Many of the associated impacts such as sea level change (among other metrics) have occurred since 1950 at rates unprecedented in the historical record.
  • There is a clear human influence on the climate
  • It is extremely likely that human influence has been the dominant cause of observed warming since 1950, with the level of confidence having increased since the fourth report.
  • IPCC pointed out that the longer we wait to reduce our emissions, the more expensive it will become.
Historical climate metrics
  • It is likely (with medium confidence) that 1983–2013 was the warmest 30-year period for 1,400 years.
  • It is virtually certain the upper ocean warmed from 1971 to 2010. This ocean warming accounts, with high confidence, for 90% of the energy accumulation between 1971 and 2010.
  • It can be said with high confidence that the Greenland and Antarctic ice sheets have been losing mass in the last two decades and that Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent.
  • There is high confidence that the sea level rise since the middle of the 19th century has been larger than the mean sea level rise of the prior two millennia.
  • Concentration of greenhouse gases in the atmosphere has increased to levels unprecedented on earth in 800,000 years.
  • Total radiative forcing of the earth system, relative to 1750, is positive and the most significant driver is the increase in CO
    2
    's atmospheric concentration.
Models
AR5 relies on the Coupled Model Intercomparison Project Phase 5 (CMIP5), an international effort among the climate modeling community to coordinate climate change experiments. Most of the CMIP5 and Earth System Model (ESM) simulations for AR5 WRI were performed with prescribed CO
2
concentrations reaching 421 ppm (RCP2.6), 538 ppm (RCP4.5), 670 ppm (RCP6.0), and 936 ppm (RCP 8.5) by the year 2100. (IPCC AR5 WGI, page 22).
  • Climate models have improved since the prior report.
  • Model results, along with observations, provide confidence in the magnitude of global warming in response to past and future forcing.
Projections
  • Further warming will continue if emissions of greenhouse gases continue.
  • The global surface temperature increase by the end of the 21st century is likely to exceed 1.5 °C relative to the 1850 to 1900 period for most scenarios, and is likely to exceed 2.0 °C for many scenarios
  • The global water cycle will change, with increases in disparity between wet and dry regions, as well as wet and dry seasons, with some regional exceptions.
  • The oceans will continue to warm, with heat extending to the deep ocean, affecting circulation patterns.
  • Decreases are very likely in Arctic sea ice cover, Northern Hemisphere spring snow cover, and global glacier volume
  • Global mean sea level will continue to rise at a rate very likely to exceed the rate of the past four decades
  • Changes in climate will cause an increase in the rate of CO
    2
    production. Increased uptake by the oceans will increase the acidification of the oceans.
  • Future surface temperatures will be largely determined by cumulative CO
    2
    , which means climate change will continue even if CO
    2
    emissions are stopped.
The summary also detailed the range of forecasts for warming, and climate impacts with different emission scenarios. Compared to the previous report, the lower bounds for the sensitivity of the climate system to emissions were slightly lowered, though the projections for global mean temperature rise (compared to pre-industrial levels) by 2100 exceeded 1.5 °C in all scenarios.

Other

The 'Next Generation Earth System Models' (e.g. HadGEM2) can produce hundreds of terabytes to perhaps tens of petabytes of climate model data for analysis.

Climate model simulations in support of AR5 use a different approach to account for increasing greenhouse gas concentrations than in the previous report. Instead of the scenarios from the Special Report on Emissions Scenarios the models are performing simulations for various Representative Concentration Pathways.

Public debate after the publication of AR4 in 2009 put the IPCC under scrutiny, with controversies over alleged bias and inaccuracy in its reports. In 2010, this prompted U.N. Secretary-General Ban Ki-moon and IPCC chair Rajendra K. Pachauri to request that the InterAcademy Council (IAC) review the IPCC and recommend ways to strengthen its processes and procedures for the preparation of AR5. The IAC report made recommendations to fortify IPCC's management structure, to further develop its conflict-of-interest policy, to strengthen the review process, to clarify the guidelines on the use of so-called gray literature, to ensure consistency in the use of probabilities for the likelihood of outcomes, and to improve its communications strategy especially regarding transparency and rapidity of response.

Current documents

Condensed versions

The Climate and Development Knowledge Network has produced region-specific toolkits for policy makers, practitioners, journalists and teachers based on the findings in the Fifth Assessment Report. They include summary reports which distill the key findings of the IPCC report; as well as media materials such as infographics, slideshow presentations and images which can be used for training, educational and reporting purposes. The four toolkits that have been developed are:

Special Report on Global Warming of 1.5 °C

The IPCC published their "Special Report on Global Warming of 1.5 °C" on October 8, 2018.

Operator (computer programming)

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Operator_(computer_programmin...