Matt Ridley: Climate Change Will Not Be Dangerous For A Long Time

  • Date: 28/11/15
  • Matt Ridley, Scientific American

Slower warming than predicted gives the world time to develop better energy technologies

The climate change debate has been polarized into a simple dichotomy. Either global warming is “real, man-made and dangerous,” as Pres. Barack Obama thinks, or it’s a “hoax,” as Oklahoma Sen. James Inhofe thinks. But there is a third possibility: that it is real, man-made and not dangerous, at least not for a long time.

This “lukewarm” option has been boosted by recent climate research, and if it is right, current policies may do more harm than good. For example, the Food and Agriculture Organization of the United Nations and other bodies agree that the rush to grow biofuels, justified as a decarbonization measure, has raised food prices and contributed to rainforest destruction. Since 2013 aid agencies such as the U.S. Overseas Private Investment Corporation, the World Bank and the European Investment Bank have restricted funding for building fossil-fuel plants in Asia and Africa; that has slowed progress in bringing electricity to the one billion people who live without it and the four million who die each year from the effects of cooking over wood fires.

In 1990 the Intergovernmental Panel on Climate Change (IPCC) was predicting that if emissions rose in a “business as usual” way, which they have done, then global average temperature would rise at the rate of about 0.3 degree Celsius per decade (with an uncertainty range of 0.2 to 0.5 degree C per decade). In the 25 years since, temperature has risen at about 0.1 to 0.2 degree C per decade, depending on whether surface or satellite data is used. The IPCC, in its most recent assessment report, lowered its near-term forecast for the global mean surface temperature over the period 2016 to 2035 to just 0.3 to 0.7 degree C above the 1986–2005 level. That is a warming of 0.1 to 0.2 degree C per decade, in all scenarios, including the high-emissions ones.

At the same time, new studies of climate sensitivity—the amount of warming expected for a doubling of carbon dioxide levels from 0.03 to 0.06 percent in the atmosphere—have suggested that most models are too sensitive. The average sensitivity of the 108 model runs considered by the IPCC is 3.2 degrees C. As Pat Michaels, a climatologist and self-described global warming skeptic at the Cato Institute testified to Congress in July, certain studies of sensitivity published since 2011 find an average sensitivity of 2 degrees C.

Such lower sensitivity does not contradict greenhouse-effect physics. The theory of dangerous climate change is based not just on carbon dioxide warming but on positive and negative feedback effects from water vapor and phenomena such as clouds and airborne aerosols from coal burning. Doubling carbon dioxide levels, alone, should produce just over 1 degree C of warming. These feedback effects have been poorly estimated, and almost certainly overestimated, in the models.

The last IPCC report also included a table debunking many worries about “tipping points” to abrupt climate change. For example, it says a sudden methane release from the ocean, or a slowdown of the Gulf Stream, are “very unlikely” and that a collapse of the West Antarctic or Greenland ice sheets during this century is “exceptionally unlikely.”

If sensitivity is low and climate change continues at the same rate as it has over the past 50 years, then dangerous warming—usually defined as starting at 2 degrees C above preindustrial levels—is about a century away. So we do not need to rush into subsidizing inefficient and land-hungry technologies, such as wind and solar or risk depriving poor people access to the beneficial effects of cheap electricity via fossil fuels.

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