The question arises: how might temperature variation have changed? We all know (if you don’t already, then read this blog!) that things like temperature show a combination of trend and fluctuation. We almost always focus on the trend, because that’s what shows the most obvious changes over time. But those fluctuations … the “noise” that we add to “signal” to get “data” … the “variation” we add to “average” to get the “weather” … are they changing too? Or are they just doing the same old same old kind of fluctuation they’ve been doing all along? This is a very different question than we usually hear about in discussion of climate change, not about a change in the average temperature, but whether or not the fluctuations have somehow changed.
They’re prominent in today’s news on two continents. The great plains of the USA are shivering through some of their coldest temperatures on record as the “polar vortex” invades from the north. Meanwhile, Australians suffer through their hottest month and worst heat waves ever, hell on earth for a place already known for it’s heat.
But mainly, it’s that polar vortex thing. Some have suggested that the rapid warming of the Arctic compared to the rest of the world, plus the dramatic decline of Arctic sea ice, have changed things in a fundamental way. It has thrown a monkey wrench into the jet stream, and during winter it can cause the polar vortex to fragment, part of it diving southward and bringing the deep freeze with it.
A certain David Weissman asked a question on twitter:
The first few answers (listed above) didn’t seem very helpful. Not to worry, David. I’m here for you.
What with Australia’s record-breaking multiple-heat-waves January, amidst talk of frying eggs on the sidewalk and melting asphalt and bats dropping dead because their brains cooked in the afternoon heat, we’ve looked at temperatures down under. We’ve noted overall warming, and the increase in the number of hot days. But we haven’t specifically looked at heat waves, which require multiple hot days in a row — usually, 3 or more, which is what we’ll go with.
The city of Adelaide, capitol of South Australia, has been in the news for setting a new record: hottest temperature in Australia ever recorded in a major city, at 46.6°C (115.9°F). It sounds a bit iffy to say “in a major city,” but I’ll let Adelaide have its day and look at its past heat waves.
Readers have recently discussed the correlation through time between global temperature on the one hand, and CO2 concentration on the other. Close examination shows that the correlation is stronger during some time intervals, weaker during others, and although it’s strong overall, there seems to be a lot happening to temperature other than mimicry of the CO2 changes.
One suggestion was to study the relationship, not with CO2 concentration, but with its logarithm. This is because climate forcing — a measure of the ultimate climate-changing impact — is proportional to the logarithm of the CO2 concentration, not to the concentration itself. The idea is to look for correlation between temperature and climate forcing — and it makes sense.
The fascinating thing is: there are many different climate forcings. A lot more than just CO2.
Some are trying to defend Judith Curry’s claim that early 20th century global warming (i.e. between 1900 and 1950) was “almost as large as the warming since 1950.” An ardent attempt from Jaime Jessup reveals a mind hard at work, trying to make the evidence fit belief.
Let me explain.
Some organizations which estimate global temperature change have been behind schedule because of the U.S. government shutdown. But the folks at the Berkeley Earth Surface Temperature project have released their figures for December’s temperature, bringing the year 2018 to a close. It was a hot one.