A friend recently made, on Facebook, what I thought was a fairly innocuous comment about a confused news story on global warming, only to get the incredulous reply, ‘What, you don't believe in Climate Change?’. This, from a correspondent who surely thinks that she's enlightened and informed on the subject. Just wow.
Leaving my friend out of it, here's what I believe:
- The planet has warmed significantly, on average, since the end, in the mid-19th century, of the Little Ice Age.
- The planet has probably warmed a little, on average, since the mid-20th century, although that picture is clouded a bit by ‘adjustments’ to the surface temperature data set. In any case, the majority of 20th-century warming happened previous to 1940, i.e. prior to the majority of human emissions of greenhouse gases.
- The warmest temperatures on record were in the 1930s.
- There has been no detectable warming since the mid-1990s (1996 or 1997 for sure, possibly back to 1993, depending on the dataset and how it is processed.)
- Human action has contributed to global warming, but changes in the greenhouse effect due to human emissions is probably less than 50% responsible. (The urban heat-island effect is a significant player, too.)
- Natural variability (e.g., the end of the Little Ice Age and changes in El Nino patterns, probably not human-induced) is a significant factor.
- BEST was a bust.
- All other things being equal, climate sensitivity to changes in greenhouse gases is logarithmic, i.e. not a straight line, and levels out at higher concentrations. In other words, climate sensitivity to increased concentrations (from present) of greenhouse gases is and will be slight.
- The overall temperature effects of increased water vapor concentrations in the atmosphere, clouds included, is at most nearly neutral. Cloud effects, plus and minus, are significant, but are on balance a strong negative feedback.
- To date, ‘climate change’ as a result of anthropogenic greenhouse gases is mostly limited to the increase in temperatures. There is no evidence that we are significantly affecting weather, much less severe-weather, patterns. There is no evidence that severe-weather patterns are changing at all. (The effects of severe weather on increasing human populations is a different question.)
- Future climate change as a result of anthropogenic greenhouse gases will be slight and practically negligible.
- All of this is consistent with the ‘97% consensus’ figure, which is substantially misreported and therefore substantially misunderstood. (For what it's worth, if the proposition is that the planet has warmed significantly since the mid-19th century and that human action has contributed to this change, then 97% is probably a significant underestimate.)
But I have this nasty habit of reading past the headline and lede, and not just getting my information from press releases and news reporters.