In this post I’m going to sum up the most important statements of the IPCC AR4 report. The reason for doing this is to have a easy to scan source for myself and everyone interested in this topic. I think it’s one of the great advantages of a blog system to easily share material you otherwise would only produce for yourself. And so other persons may benefit from it, too. I’d appreciate any of your comments
The full report from which the following summary is created can be found at: http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf
Observation of climate change
- Definition (climate change): all changes of climate state observed over longer time periods (decades or longer)
- Warming of global temperatures: widespread, greatest at higher latitudes, warming over land greater than warming over oceans, ocean has been taking up over 80% of the
heat being added to the climate system
- Sea level rising: 1.8mm per year on average (1961-2003)
(over 50 percent contribution due to thermal expansion)
- Decrease in snow/ice extent in both hemispheres (annual average Arctic sea ice extent has shrunk by 2.7% per decade)
- Trends in precipitation observed between 1900 and 2005:
- increase: eastern parts of North and South America, northern Europe, central Asia
- decrease: Sahel, Mediterranean region, southern Africa and southern Asia
- Extreme weather events:
- high chance for less cold days and nights, while the chance for warmer days and nights and heat waves over land will increase.
- Likely increasing tropical storm occurrence in North Atlantic region since 1970
Observed Effects of climate change
- High confidence that permafrost regions influenced
- Very high confidence for earlier spring events
- Shifts in ranges and changes in algal, plankton and fish abundance in high-latitude oceans.
- More effects likely but not easy to distinguish the climate influence from other influence sources.
- Antarctic sea ice shows no clear longterm trend, only inter-annual variations.
- No clear trends for small-scale features.
to be continued… (soon)
Last modified: November 5, 2011