The summary for policymakers (PDF) of the report by the IPCC Second Working Group is out!

A summary of the summary:

Where does the information come from?

  • The IPCC, WGI’s 4AR on the Scientific Basis of climate change.
  • 29,000 observational data series crossed with expected changes to physical and biological systems based on those observations, with 89% consistency between the two.
  • Models, some of which account for non-anthropogenic sources of warming (solar and volcanic activity) and others that do not. The results show that, “models with combined natural and anthropogenic forcings simulate observed responses significantly better than models with natural forcing only.”

What are some of the major conclusions?

Grist thanks its sponsors. Become one.

There is very high confidence (9 out of 10), based on more evidence from a wider range of species, that recent warming is strongly affecting terrestrial biological systems, including such changes as:

  • earlier timing of spring events, such as leaf-unfolding, bird migration and egg-laying;
  • poleward and upward shifts in ranges in plant and animal species.

There is high confidence (8 out of 10) that the following changes are occurring due to warming:

Grist thanks its sponsors. Become one.

  • in terms of snow, ice and frozen ground (including permafrost), there is increased instability in such terrain and larger glacial lakes;
  • relating to hydrological systems, there are warmer lakes and increased and earlier run-off earlier greening of vegetation and longer growing seasons;
  • in marine and freshwater biological systems, there is rising water temperatures, as well as related changes in ice cover, salinity (water content is more acidic), oxygen levels and circulation.

Effects of temperature increases have been documented in the following systems (medium confidence)”:

  • effects on agricultural and forestry management at Northern Hemisphere higher latitudes, such as earlier spring planting of crops, and alterations in disturbance regimes of forests due to fires and pests;
  • some aspects of human health, such as heat-related mortality in Europe, infectious disease vectors in some areas, and allergenic pollen in Northern Hemisphere high and mid-latitudes;
  • some human activities in the Arctic (e.g., hunting and travel over snow and ice) and in lower elevation alpine areas (such as mountain sports).”

Generally speaking, how can we proceed to deal with the changes:

  • “Adaptation will be necessary to address impacts resulting from the warming which is already unavoidable due to past emissions.”
  • “Many impacts can be avoided, reduced or delayed by mitigation.”
  • “A portfolio of adaptation and mitigation measures can diminish the risks associated with climate change.”

Oh, and, buried in the report, to make up for that huge hole about Greenland and the Antarctic in February’s report:

Very large sea-level rises that would result from widespread deglaciation of Greenland and West Antarctic ice sheets imply major changes in coastlines and ecosystems, and inundation of low-lying areas, with greatest effects in river deltas. Relocating populations, economic activity, and infrastructure would be costly and challenging. There is medium confidence that at least partial deglaciation of the Greenland ice sheet, and possibly the West Antarctic ice sheet, would occur over a period of time ranging from centuries to millennia for a global average temperature increase of 1- 4°C (relative to 1990-2000), causing a contribution to sea level rise of 4-6 m or more. The complete melting of the Greenland ice sheet and the West Antarctic ice sheet would lead to a contribution to sea-level rise of up to 7 m and about 5 m, respectively.