Re: “Who doesn’t trust science now?” Feb. 17 David Harsanyi column.
Deniers of global warming and climate change frequently argue that the Earth has cooled over the past decade. This conclusion involves cherry-picking the data. True, if one picks the beginning and end of the 1998-2007 decade, a 0.3-degree (Fahrenheit) cooling trend in the average global temperature can be inferred. However, if one instead moves that window to 1997-2006, there has been a 0.6-degree warming trend. Both interpretations are misleading.
The difference? Climate fluctuations. During 1998-99, there was a sharp spike in the average global temperature due to the combined effects of a strong El Niño oscillation and the onset of a cycle of increased solar irradiation. Until recently, the post-1999 global temperature has remained relatively constant, about 0.4 degrees above the average for 1988-97. However, if the 1998-99 anomaly should recur — which may be indicated by the observed 1.2-degree increase since January 2008 — it could signal an upsurge in global temperatures.
When El Niño and solar cycle effects are factored out of the data, the results show a steady increase of about 0.9 degrees over the past 30 years. Coupled with the 16 percent increase in atmospheric CO2 during this period, the data strongly suggest human activity as the source of the observed temperature rise.
Land-based observations are subject to strong variations. While those east of the Rockies and in Europe have experienced a colder than usual winter, the rest of the planet has been much warmer. Three-fourths of the Earth is covered by water, which undergoes much more moderate temperature variations and plays a major role in regulating the global climate. At present, thousands of weather buoys monitor global ocean temperatures, which, along with detailed satellite data, feed into the global average temperature calculations.
Another point deniers make is that in the 1970s, some scientists predicted the Earth was cooling. A more accurate statement is that both the cooling and warming scenarios were in play then. Questions about the cooling effects of aerosols from volcanoes, power plants, etc., had to be weighed against possible warming due to increases in greenhouse gases. Since the 1970s, there has been a dramatic increase in climate-related research, abetted by much more sophisticated measurement techniques and equipment.
We now have the benefit of a 40-year experiment upon which to base our conclusions. The bottom line — supported by the National Academy of Sciences and numerous scientific societies — is that global warming and climate change due to human activity is real and poses a serious threat to the future of our planet.
Vic Viola (viola@indiana.edu) is a distinguished professor emeritus at Indiana University and lives in Golden.
