The report we've all been waiting for is in.
(Drum roll please...)
The Intergovernmental Panel on Climate Change (IPCC) has just released the Fourth Assessment Report on climate change (the
20pg summary for policy makers is available for download online.) Note to policy makers: GO READ IT! Everyone else can check out the
NYTimes article.
The last report (or rather the basis for much of the contrived controversy over the past five years on the topic) was issued in 2001.
Here's a few highlights:
Since the Third Assessment Report (TAR), new observations and related modelling of greenhouse gases, solar activity, land surface properties and some aspects of aerosols have led to improvements in the quantitative estimates of radiative forcing.... Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years (see Figure SPM-1). The global increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change, while those of methane and nitrous oxide are primarily due to agriculture.
If I'm not mistaken I think they just said "human activities" (upon rereading I do see that it does in fact mention human activities are responsible - wow that's a bold statement.)
Oh, look here, where the scientist consortium says with emphasis that the planet is in fact warming:
The understanding of anthropogenic warming and cooling influences on climate has improved since the Third Assessment Report (TAR), leading to very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming, with a radiative forcing of +1.6 [+0.6 to +2.4] W m-2.
Here's the bit where they confirm sea levels are rising:
Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level.
And expanding on that:
Eleven of the last twelve years (1995 -2006) rank among the 12 warmest years in the instrumental record of global surface temperature9 (since 1850). The updated 100-year linear trend (1906–2005) of 0.74 [0.56 to 0.92]°C is therefore larger than the corresponding trend for 1901-2000 given in the TAR of 0.6 [0.4 to 0.8]°C. The linear warming trend over the last 50 years (0.13 [0.10 to 0.16]°C per decade) is nearly twice that for the last 100 years. The total temperature increase from 1850 – 1899 to 2001 – 2005 is 0.76 [0.57 to 0.95]°C. Urban heat island effects are real but local, and have a negligible influence (less than 0.006°C per decade over land and zero over the oceans) on these values. {3.2}... 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.
Here's the part where they link in some weather changes (noting that not ALL weather patterns are changing however):
More intense and longer droughts have been observed over wider areas since the 1970s, particularly in the tropics and subtropics. Increased drying linked with higher temperatures and decreased precipitation have contributed to changes in drought. Changes in sea surface temperatures (SST), wind patterns, and decreased snowpack and snow cover have also been linked to droughts. The frequency of heavy precipitation events has increased over most land areas, consistent with warming and observed increases of atmospheric water vapour. Widespread changes in extreme temperatures have been observed over the last 50 years. Cold days, cold nights and frost have become less frequent, while hot days, hot nights, and heat waves have become more frequent (see Table SPM-1). There is observational evidence for an increase of intense tropical cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface temperatures.
Then they put it in a paleoclimactic perspective:
Paleoclimate information supports the interpretation that the warmth of the last half century is unusual in at least the previous 1300 years. The last time the polar regions were significantly warmer than present for an extended period (about 125,000 years ago), reductions in polar ice volume led to 4 to 6 metres of sea level rise.
And again, back to the human factor (as if we didn't feel guilty enough as it is...):
Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.
This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”. Discernible human influences now extend to other aspects of climate, includin ocean warming, continental average temperatures, temperature extremes and wind patterns.
And for those of you who are still caught up on the volcanic eruption/natural occurrence thing:
It is likely that increases in greenhouse gas concentrations alone would have caused more warming than observed becaushave taken place. The observed widespread warming of the atmosphere and ocean, together with ice mass loss, support the conclusion that it is extremely unlikely that global climate change of the past fifty years can be explained without external forcing, and very likely that it is not due to known natural causes alone.
Then there's the magic 8 ball predictions for the future: the snow cover will decrease; sea ice will also decrease; expect more high heats, extreme rains, and tropical cyclones; sea levels will rise (mostly attribued to the Greenland melt); but hey, good news the Antarctic ice sheet is too cold for widespread surface melting.
Of course, these are just a few select excerpts (although it does feel like I copied and pasted the whole thing.) There are some great graphs and maps on the final few pages.
But what is the significance of this report?
Basically they're saying that things haven't gotten better since the last report, only this time, instead of taking the tone that "we're pretty sure this is happening," the fourth assessment is more of a "we're pretty DAMN sure this is happening - now policymakers get off your arses and do something about it!!"
Now can we PLEASE officially call the debate over and get going on some real action?
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