IPCC summaries


in Science, The environment

Pretty much everyone has read news coverage on climate change, but it seems that relatively few people have read anything the IPCC has actually written. I recommend looking over the 21 pages of the Summary for Policymakers for the Fourth Assessment Report (PDF). It addresses a number of topics covered in the media, from global dimming to variations in solar output.

While few people who read it are personally qualified to gauge its accuracy, and even those who could would need the information from the full report text, it is nonetheless worthwhile to look at the source, rather than the versions processed by the BBC or the New York Times.

For those wanting to track what has changed over the last six years, within the IPCC’s conclusions, have a look at the surprisingly brightly coloured Summary for Policymakers from the Third Assessment Report. Note that, unlike the full reports, the summaries are vetted line-by-line by representatives from member governments.

{ 6 comments… read them below or add one }

Milan March 20, 2007 at 12:42 pm

Commentary on global dimming is on p. 3, 8, and 16 of the summary

Changes in solar output are mentioned on p. 3 and 16

Anonymous March 21, 2007 at 2:28 pm

“Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80% of the heat added to the climate system. Such warming causes seawater to expand, contributing to sea level rise.”

Will the ocean keep absorbing heat in a linear way, or will it eventually get saturated somehow?

Anonymous March 21, 2007 at 2:32 pm

The Emission Scenarios they list are quite interesting:

A1. The A1 storyline and scenario family describes a future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies. Major underlying themes are convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income. The A1 scenario family develops into three groups that describe alternative directions of technological change in the energy system. The three A1 groups are distinguished by their technological emphasis: fossil intensive (A1FI), non-fossil energy sources (A1T), or a balance across all sources (A1B) (where balanced is defined as not relying too heavily on one particular energy source, on the assumption that similar improvement rates apply to all energy supply and end use technologies).

A2. The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is self reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing population. Economic development is primarily regionally oriented and per capita economic growth and technological change more fragmented and slower than other storylines.

B1. The B1 storyline and scenario family describes a convergent world with the same global population, that peaks in mid-century and declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives.

B2. The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels.

R.K. March 23, 2007 at 4:27 pm

You may as well link the Stern Report too:

full version
executive summary

. September 22, 2008 at 4:35 pm

From the Technical Summary of the Working Group I section of the Fourth Assessment Report of the IPCC:

‘Global dimming’ is not global in extent and it has not continued after 1990. Reported decreases in solar radiation at the Earth’s surface from 1970 to 1990 have an urban bias. Further, there have been increases since about 1990. An increasing aerosol load due to human activities decreases regional air quality and the amount of solar radiation reaching the Earth’s surface. In some areas, such as Eastern Europe, recent observations of a reversal in the sign of this effect link changes in solar radiation to concurrent air quality improvements.

. June 1, 2014 at 10:28 am

Since the report’s publication, more unseemly wrangles have come to light. Robert Stavins, a professor at Harvard University and a lead author on the chapter in the main report dealing with international co-operation, wrote to the report’s chairman “to express my disappointment and frustration”. As he pointed out, most of the delegates to the IPCC are in the middle of negotiating a treaty, intended to be signed in Paris in 2015, limiting greenhouse-gas emissions. As Dr Stavins says, “any text that was considered inconsistent with their interests and positions in multilateral negotiations was treated as unacceptable.” It was not necessary that they should all find something objectionable. The requirement of unanimity meant one country was enough. Three-quarters of his original draft was rejected and what remains is a list of disconnected facts, not a guide to the state of knowledge.

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