It is a good article but a lousy headline. The December 7 issue of New Scientist has a cover head-line “Climate showdown: Is it time to stop worrying about global warming?“ That will create the wrong impression among those many people who get no further than headlines. And it certainly doesn’t convey the message of the article itself.
The article does acknowledge that “the average surface temperature of the planet seems to have increased far more slowly over [recent years] than it did over the precious decades.”
“This doesn’t mean that climate change has stopped, any more than the very rapid warming seen in the 1990s meant it had accelerated.”
The article a describes several reasons that help explain the current situation. To do this it stresses “it helps to think about heat energy rather than temperature.” In summary:
“In terms of heat. There are three possible reasons why the Earth’s surface temperature hasn’t increased much recently”
- Less heat arriving from the sun. “The sun’s heat output rises and falls in an 11-year cycle and measurements by spacecraft such as SOHO show it did dip particularly low recently.”
- Increased levels of sulphur aerosols in the atmosphere could have reflected more of the sun’s heat back into space. “Levels of sulphur dioxide have risen in the past decade, mainly due to lots of small volcanic eruptions.”
- More of the heat gained by the planet “ends up somewhere other than the lower atmosphere, whose temperature we focus on.”
Ocean – the main culprit
The article points out the most likely storage place for this heat is the ocean.
“Water covers more than 70% of the planet and the stuff has a huge capacity to absorb heat: around 3000 times as much energy is needed to warm a given volume of water by 1°C as is needed to warm the same volume of air.
“Observations show that a whopping 94% of the heat energy gained by the planet since 1971 has ended up in the oceans, with another 4% absorbed by land and ice. . . . So all the surface warming since 1971 is due to just 2 per cent of the heat. If just a little more heat than usual has been going into the oceans, it will have had only a slight effect on ocean surface temperatures, because of water’s huge capacity to absorb heat, but a large effect on atmospheric temperature. And several studies show that the oceans have indeed been soaking up even more heat than normal.”
The article goes on to suggest this is because there have been lots of La Niňas (which cause the Pacific to soak up heat – thus cooling the planet) lately but no major El Niňo (which extract heat from the Pacific to the atmosphere and warm the planet) for the past 15 years.
The graphic from the article illustrates where the heat has gone.
The whole process is obviously complicated and there are various opinions among climate scientists about the relative importance of the different processes distributing heat. There is even a suggestion “that soaring aerosol emissions from China may have contributed to the slowdown” of surface temperature increases. However:
“the mainstream view expressed in the latest Intergovernmental Panel on Climate Change report is that about half of the surface slowdown is due to the oceans, and the other half due to the sun and extra volcanic aerosols.”