It’s Still With Us

I received two brief letters last Monday from C&EN readers, both containing the same clipping of an op-ed piece that appeared in the Sept. 6 Wall Street Journal. The essay by Matt Ridley, the author of a number of well-reviewed books on scientific and economic topics, is entitled “Whatever Happened to Global Warming?”

The gist of the essay is that global warming has paused for the past 15 years—global surface temperature hasn’t increased appreciably since 2000—and that this suggests climate change isn’t really all that big a deal and we should focus, Ridley writes, on “more pressing global problems like war, terror, disease, poverty, habitat loss, and the 1.3 billion people with no electricity.”

In his brief handwritten letter, ACS member Anthony Pavone wrote: “Rudy, Although I’m sure that you still dispute the conclusions, I believe that you have an obligation to present the data.”

I agree. The plot on this page is from a “News & Views” article by Isaac M. Held, a researcher in the Geophysical Fluid Dynamics Laboratory at the National Oceanic & Atmospheric Administration, that appeared last year in Nature (2013, DOI: 10.1038/501318a). It shows the global mean surface temperature relative to the 1961–90 mean. The data are from the Climate Research Unit of the University of East Anglia. The title of Held’s essay is “The Cause of the Pause.”

The inset on the graph shows the 1993 to 2012 time span, with the green points corresponding to La Niña years and the red, El Niño years. The reason these are highlighted is because in a paper in the same issue of Nature (DOI: 10.1038/nature12534), Scripps Institution of Oceanography researchers Yu Kosaka and Shang-Ping Xie present a case that these phenomena can account for the pause in global warming.

They write: “Despite the continued increase in greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming. … Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations.”

Essentially, Kosaka and Xie show that by considering the observed history of sea-surface temperature over a portion of the Pacific Ocean in addition to radiative forcing, their model “reproduces the annual-mean global temperature remarkably well … for 1970–2012 (which includes the current hiatus and a period of accelerated global warming).”

You see, climate scientists are well aware of this climate anomaly, and they’re not trying to hide it. The pause does not, as Ridley suggests, invalidate climate models that show we are playing a dangerous game with Earth’s climate.

There’s another important feature of the graph—global temperature isn’t coming down. The rise in temperature has simply paused. Every year in the past decade has been one of the warmest on record since 1850. And there is no evidence whatsoever in these data to suggest that global temperature is going to do anything but increase in the coming years.

The recent World Meteorological Organization (WMO) Greenhouse Gas Bulletin reported that levels of atmospheric CO₂, CH₄, and N₂O reached new highs in 2013, with CO₂ at 396 ppm, CH₄ at 1,824 ppb, and N₂O at 326 ppb. Climate disruption is still very much with us.

Thanks for reading.