IPCC Third Assessment Report

The Third Assessment Report of the IPCC (English: Third Assessment Report TAR ) summarized in 2001, then the evidence for global warming together. He was released by the Intergovernmental Panel on Climate Change, which is to assess the risks of these climate change on behalf of the United Nations and designing prevention strategies.

He was replaced in 2007 by the Fourth Assessment Report, which confirmed the main points of the third and has since served as the basis for the discussion about climate change.

Publication

The progress report was published in four parts. The three main scientific works were completed in the first quarter of 2001 and presented. The particularly intense coordinated summary was confirmed at the IPCC plenary meeting of 24 to 29 September 2001, both by the researchers as well as by representatives of the signatories to the UNFCCC and published on 1 October 2001.

Content

The report does not own research, but it includes a large number of scientific publications, which each have already been discussed and examined for themselves ( peer review ), together.

Climate development in the 20th century and their consequences

The concentrations of carbon dioxide, methane, nitrous oxide, halocarbons and sulfur hexafluoride in the atmosphere have increased clearly. This results in a measurable increase in atmospheric back-radiation and thereby to heat. There is evidence ( "strong evidence" ) that this is due to human action.

The progress report notes that the average global temperature has increased by about 0.6 K during the 20th century. The 1990s were the warmest decade and 1998 the warmest year since the beginning of the systematic temperature measurements in the southern hemisphere in 1861. Precipitation has increased on the whole world, the number of frost days and the size of the ice fell on all continents. Rivers and lakes in the northern hemisphere are due two weeks less on average covered with ice as the beginning of the century, snow and ice have fallen by 10 percent since 1960.

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

Scenarios for development in the 21st century

For the 21st century, four main scenarios are designed. In the A- scenarios, the economic development with maximum monetary wealth in the foreground, in the B scenarios, the greening is assumed. Variants 1 to accept that the world is united economically and politically and in particular efficient technologies are available worldwide; in the 2- scenarios a regionally separate development is required. The A1 scenario is still divided into variants with different available energy sources. For all combinations of the likely emissions are assumed and modeled the possible consequences, especially the carbon dioxide concentrations and temperature development. Depending on the assumptions, there is for the period up to 2100, a temperature rise of between 1.4 ° C ( B1 scenario) and 5.8 ° C (A1 with the longest possible holding of fossil fuels ) compared to 1990. Doing so, the land areas warm more and faster than the oceans. The heating is also on completion of greenhouse gas emissions continue to increase for several centuries until land and oceans have warmed throughout.

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

The sea level will rise in the 21st century, 9-88 cm and continue this rise for centuries, possibly millennia, in a row. Peak and minimum temperatures will rise to nearly all land areas. The precipitate continues to increase, but also drier summers are likely. Biodiversity is changing and it will die out additional species, but more concrete statements are uncertain. Food production may rise regionally, but globally fall significantly over wide variations. The consequences for the world economy as a whole are more negative, but not sure to judge ("low confidence" ), developing countries relative to their opportunities significantly more affected than industrialized countries.

Recommendations

The undesirable consequences can be consistently delayed and partially prevented when the emission of greenhouse gases is lowered.

In addition, people need to adapt to the already triggered and no longer completely unstoppable warming.

Although both the abatement costs and the level of the still avoidable damages are uncertain, it is foreseeable that the avoidance of emissions is economically the more rewarding decision.

Criticism

As part of the controversy surrounding global warming, the report was criticized several times. Critics such as the co-author and meteorologist Richard Lindzen saw uncertainty and need for further research in a number of respects, the existing climate models are not sufficient to consider the results as safe.

Much of the criticism was aimed at a reconstruction of temperatures in recent centuries, known for their in the late 19th century upward bend of course " hockey stick graph ". Was controversial case in the matter, whether it was warmer or colder than in the 1990s during the medieval warm period and whether therefore located humanity still within a " natural" temperature range. In later investigations and studies the major criticisms of the hockey stick graph could be refuted, even if temperature reconstructions remain connected for the period before 1600 with uncertainties.