Are current heatwaves evidence that climate change is speeding up? The Economist tries to answer the question

Are the current heatwaves evidence that climate change is speeding up? That's the headline over a comprehensive article in The Economist, with a subhead, "All sorts of records are being broken in all sorts of places." Yes, it;'s July, but "the highest temperatures tend to come later in the season. That this year’s should start so early, rise so high and run so long is unprecedented."

The British magazine notes the basic drivers: Carbon dioxide in the atmosphere is "the highest it has been for over 3 million years. Methane and nitrous oxide, two other long-lived greenhouse gases, have also reached levels never before experienced by humans. The world is now, on average, around 1.2°C warmer than it was before humans started thickening the glass in the greenhouse."

James Hansen of Columbia University, a climate scientist who was one of the first to warn of global warming, "argues that the rate at which the world is warming seems to have gone through a step change in the 2010s, though he has not yet convinced his peers. This summer’s surprises, especially a run of record temperatures in the North Atlantic, might help change that."

An El Niño began last month, which has a warming effect, but such ocean oscillations tend to have their greatest impact about a year in, and "Today’s ocean temperatures look like evidence of this one getting off to a flying start." Another likely factor is the huge eruption of a submarine Pacific volcano last year, which  injected a huge amount of water vapor, a powerful greenhouse gas, into the air. "In the lower atmosphere it condenses out into rain or snow fairly quickly. In the stratosphere, though, it lingers for longer," The Economist notes, adding that trhe eruption "is thought to have increased the amount of water vapor in the stratosphere by 13%."

We'v heard more lately about methane, a very powerful greenhouse gas, and "Some scientists cite recent increases in methane levels as evidence" that the world is warming in much the same way it did at the end of the last ice age. Some think it's because there are more tropical wetlands, "whose plants produce the gas when they rot. This is one candidate for the mechanism that drives the methane spikes seen at the end of ice ages. If true, it opens up the possibility of a feedback loop starting today similar to the ones that seem to have operated in the past. More methane means more warming, which means more wetlands, and therefore more methane."

Also, government limits on sulfur dioxide to quash acid rain and a more recent change to reduce pollution from ocean shipping may have cause more warming. Sulphate particles that SO2 creates in the lower atmosphere reflect sunlight, and "can help create clouds which reflect away more sunshine still." However, "The indirect effects that aerosol particles have on cloud cover are notoriously hard to capture in climate models."