Would we recognize Xtreme Weather if it walked up and greeted us? Is our weather special?
Kevin Trenberth is trying (and to a large extent succeeding) to convince the world that today’s weather is a product of climate change–that what we see around is the weather we have to a large extent created. In particular, extreme events are more frequent and more extreme because we have both warmed the planet and added moisture to the atmosphere.
Is this true? I intend to spend some time looking through published statistics and will produce the inevitable mind-numbing series of charts both supporting and opposing the premise.
But what really is the premise? Is a normal day today different from a normal day of 75 years ago? (I say 75 because the modern warming laid to greenhouse gases is variously said to have commenced around 1945.)
Is Trenberth saying that a storm with X energy today would have been a storm of X-y% 75 years ago? That if we have 16 hurricanes in the Atlantic this year we would have had 14 75 years ago?
Now Trenberth writes that “If the problem is generalized to look at the entire probability distribution function (pdf) of the climate variables, then the biggest changes percentagewise occur in the tails of the distribution, where they can easily exceed several hundred percent (Trenberth 2011b). Accordingly, a change in climate is most likely to be perceived by encountering new “weather” and breaking records: changes in the extremes. Changes in certain extremes, such as higher temperatures and increases in heavy rains and droughts are expected with climate change (IPCC 2007; Trenberth 2011a).
But to me he’s saying just that extremes are easier to notice–not that only extremes are expected.
I’d really like to know what it would take to either prove or disprove his thesis. Many people have already addressed his claims regarding weather extremes, and although I’m happy to bring them all into one place with whatever commentary I can provide, I’m not sure how much value that adds. Can someone please plausibly explain to me:
What changes should we expect to see in both normal and extreme weather from 0.8C of warming and an additional 4% of moisture in the atmosphere, which he cites as observed phenomena?
Otherwise we get garbage like a post on Joe Romm’s weblog saying that the U.S. faces a $188 billion price tag from Xtreme Weather from 2011 to 2012. (The trick is that all damages from extreme weather are laid at global warming’s doorstep–because we never had extreme weather before global warming, obviously.)
I’m willing to look at variation in the length of growing seasons, variations in migration of species, precipitation records, drought records by region and storm records where they exist. But what if we find nothing unusual?
When all storms are special–remembering Dash’s preternaturally wise observation above–none will be.