Third progress report by the IPCC

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The third assessment report of the IPCC ( English : Third Assessment Report TAR ) in 2001 summarized the then available findings on global warming . It was published by the Intergovernmental Panel on Climate Change , which, on behalf of the United Nations, is to assess the risks of this climate change and develop strategies for avoiding them.

It was replaced in 2007 by the fourth assessment report , which confirmed the core statements of the third and since then has served as the basis for the discussion on climate protection .

publication

The progress report was published in four parts. The three main scientific works were completed and presented in the first quarter of 2001. The particularly intensely coordinated summary was confirmed at the IPCC General Assembly from September 24 to 29, 2001 both by the participating scientists and by the representatives of the signatory states to the Framework Convention on Climate Change and published on October 1, 2001. A total of more than 600 climate researchers were involved as authors on the report, and it was also examined by around 400 reviewers .

Content

The report does not contain its own research results, but rather summarizes a large number of scientific publications, each of which has already been discussed and examined ( peer review ).

Climate development in the 20th century and its consequences

The concentrations of carbon dioxide , methane , nitrous oxide , halogenated hydrocarbons and sulfur hexafluoride in the earth's atmosphere have clearly increased. This leads to a measurably increased atmospheric counter-radiation and thus to heating. There are clear indications ( “strong evidence” ) that this is due to human activity.

The status report states that the global average temperature has increased by around 0.6 K over the course of the 20th century. The 1990s were the warmest decade and 1998 the warmest year since systematic temperature measurements began in the southern hemisphere in 1861. Overall, precipitation has increased worldwide, the number of frost days and the size of the ice sheets have declined on all continents. Rivers and lakes in the northern hemisphere are on average two weeks less covered with ice than at the beginning of the century, and snow and ice areas have decreased by 10 percent since 1960.

The warming and its consequences are not only due to known natural causes, but can be explained well together with natural and human influences.

Scenarios for Development in the 21st Century

Four main scenarios are designed for the 21st century . In the A scenarios, the focus is on economic development with maximum monetary prosperity, in the B scenarios a more ecological orientation is assumed. Variants 1 assume that the world is economically and politically united and, in particular, that efficient technologies are available worldwide; a regionally separate development is assumed in the two-part scenarios. The A1 scenario is still divided into variants with different available energy sources. The probable emissions are assumed for all combinations and the possible consequences, in particular the carbon dioxide concentrations and the temperature development, are modeled. Depending on the assumptions, a temperature increase between 1.4 ° C (B1 scenario) and 5.8 ° C (A1 with the longest possible adherence to fossil fuels ) compared to 1990 results for the period up to 2100. The land areas are warming faster and more than the oceans. The warming will continue to increase for several centuries even after greenhouse gas emissions have ceased, until land areas and oceans have warmed up consistently.

Based on these temperature changes, the probable and possible consequences such as extreme weather, sea ​​level rise and the economic risks are considered.

Sea levels will rise between 9 and 88 cm in the 21st century and this rise will continue for centuries, possibly millennia, in a row. Peak and low temperatures will rise on almost all land areas. Precipitation continues to increase, but drier summers are also likely. The biodiversity will change and it will become extinct additional species, but more concrete statements are uncertain. Food production can increase regionally, but will decrease significantly globally if there are significant changes. The consequences for the global economy as a whole are rather negative, but cannot be assessed with certainty ( "low confidence" ) . Developing countries are affected significantly more than industrialized countries relative to their possibilities .

recommendations

The undesirable consequences can all be delayed and partially avoided if greenhouse gas emissions are reduced.

In addition, people have to adapt to the warming that has already been triggered and can no longer be completely stopped.

Although both the avoidance costs and the amount of avoidable damage are uncertain, it is foreseeable that avoiding emissions is economically the more profitable decision.

criticism

The report was heavily criticized by climate change deniers and skeptics . Critics such as co-author and meteorologist Richard Lindzen saw uncertainties and the need for further research on a number of points; the existing climate models were not sufficient to consider the results as reliable.

Various reconstructions of the global average temperature of the last millennium, including the hockey stick work in blue

Much of the criticism was directed towards a reconstruction of the temperatures in the last few centuries, which is known as the " hockey stick diagram " because of its upward curve in the late 19th century . One point of criticism was whether it was warmer or colder than in the 1990s during the medieval warm period and whether mankind is still within a “natural” temperature range. In later investigations and studies, the most important points of criticism of the hockey stick diagram could be refuted, even if temperature reconstructions for the period before 1600 remain associated with uncertainties. By 2013, 12 more historical temperature reconstructions had appeared, all of which basically confirmed the hockey stick diagram. Michael E. Mann as the main author of the graphic is hostile to climate deniers to this day because of the graphic and had to endure numerous attacks on his research and his credibility. Among other things, the deputy in holding the House of Representatives , Joe Barton 2005, a hearing in the House, which had the goal to refute the hockey stick controversy and thus to discredit the IPCC.

Web links

• IPCC Third Assessment Report (English)
• German summary on the IPCC homepage

Individual evidence

1. ↑ Mojib Latif : Are we getting the climate out of sync? Background and forecasts. Fischer-Taschenbuch-Verlag, Frankfurt 2007, pp. 135f.
2. ^ Committee on Surface Temperature Reconstructions for the Last 2,000 Years, National Research Council (2006): Surface temperature reconstructions for the last 2,000 years . Washington, DC: National Academies Press ; on-line
3. ^ Eugene Wahl, David Ritson and Caspar Ammann (2006): Comment on "Reconstructing Past Climate from Noisy Data" , in: Science , Vol. 312, No. 5773, p. 529
4. ^ Eugene Wahl and Caspar Ammann (2007): Robustness of the Mann, Bradley, Hughes reconstruction of Northern Hemisphere surface temperatures: Examination of criticisms based on the nature and processing of proxy climate evidence , in: Climatic Change , Vol. 85, No. 1, pp. 33-69
5. ↑ See G. Thomas Farmer, John Cook : Climate Change Science. A modern synthesis. Volume 1 - The Physical Climate. Dordrecht 2013, p. 14f.
6. ^ G. Thomas Farmer, John Cook: Climate Change Science. A modern synthesis. Volume 1 - The Physical Climate. Dordrecht 2013, p. 455.
7. ^ Riley E. Dunlap, Aaron M. McCright: Organized Climate Change Denial. In: John S. Dryzek, Richard B. Norgaard, David Schlosberg (Eds.): The Oxford Handbook of Climate Change and Society. Oxford University Press, 2011, pp. 144-160, p. 153.