Klimaforandringerne er ikke teori mere.
Det håber jeg ikke at der er nogen rationelle mennesker der vil argumentere imod. Klimaet har altid forandret sig og vil altid gøre det, både på kortere og længere tidsskalaer. Ideen om et uforanderligt klima er alene en tankekonstruktion.
Jeg tror heller ikke at der er mange som vil argumentere imod at vi lever i en varm periode i moderne tid og at det sidste ti år har været varmere end mange af dem som gik forud. For Grønlands indlandsis, så enten smelter den eller tager på. Den er aldrig stabil. Men vi er først lige begyndt at forske i dynamikken i gletschere, og samtidig er der stor usikkerhed omkring hvordan massetab fra et område som indlandsisen beregnes.
Så vi skal passe på med at drage forhastede konklusioner, for vi har kun pålidelige data fra en meget kort periode, og selv de data vi har i dag er for nogle områder behæftet med stor usikkerhed. I forhold til de sidste 450.000 år, så er 10-20-30 år med gode observationer en meget kort periode at drage konklusioner ud fra.
På den baggrund så vil der være klimarekorder og ekstremer. Men alt det spåede ekstreme vejr, som orkaner, tornadoer, regn osv har glimret ved sit fravær, som jeg har argumenteret for i en tidligere post:
http://ing.dk/artikel/118517-e...vejr
For dem som er interesserede i mere info om det, så har Judith Curry et glimrende indæg om netop det (og det er hendes speciale, så få det på første hånd):
I have been completely unconvinced by any of the arguments that I have seen that attributes a single extreme weather event, a cluster of extreme weather events, or statistics of extreme weather events to anthropogenic forcing.
http://judithcurry.com/2011/06...ing/
Omkring oversvømmelser har hun en hår dom over Kevin Trenberths udlægning (En af teamet - ham med The Missig Heat):
So what is wrong with the picture that Kevin Trenberth (and others) have been painting (besides the fact that they don’t seem to have looked at actual flood data)? An increase in atmospheric water vapor associated with warmer temperatures doesn’t necessarily increase rainfall nor is it necessary that an increase in rainfall is distributed spatiotemporally to produce increased floods. It seems that whatever signal that might be found for an increase in floods from global warming is swamped by changes in land use and river engineering.
Og Pielke Jr. har også noget at sige om samme:
The IPCC [Intergovernmental Panel on Climate Change] defines “climate change” as a change in the statistics of weather occurring over 30 years or longer and persisting for decades. Thus, the detection of a change in climate requires long-term records. To suggest that particular extreme weather events are evidence of climate change is not just wrong, but wrongheaded — every bit as much as the claims made during a particularly cold and snowy winter (or even several in a row) that such events somehow disprove climate change. Weather is not climate and short-term climate variability is not climate change.
The detection of changes in climate requires looking at actual data — and the data on tornadoes, large-scale river floods (in unaltered river basins), and landfalling hurricanes shows no evidence of trends in the direction of more extreme events. This should not be surprising, because even if we assume a strong signal in extreme events from human-caused climate change, the statistics suggest that it would take many decades, and probably longer, before such signals would be detected.
Given this context, claims that particular events can be attributed in a causal fashion to human emissions of greenhouse gases are simply unscientific if not fundamentally incoherent. It is true that overall damage from tornadoes, floods, and hurricanes has been increasing in recent decades. A recent literature review of extreme event impacts around the world found that everywhere that researchers have looked, this increase can be entirely explained by increasing value of property at risk and increasing exposures to these hazards.
http://e360.yale.edu/feature/f...411/
Vh Troels