Reading today's headlines, you might think that a healthy, evenly matched debate is thriving between scientists who believe human-created carbon dioxide causes global warming and those who challenge that belief. The reality is that the skeptics represent the merest tip of the iceberg (so to speak) within the scientific field of climate change. Since 2007 no reputable scientific body has rejected the basic principle that global warming is human-caused.
It's pretty easy to see why. As the concentration of CO2 has risen, from about 300 ppm (parts per million) in 1910 to the present concentration of 390 ppm, so has the mean global temperature (see graph). CO2 is an efficient greenhouse gas, allowing sunlight to pass through unimpeded while trapping the longer-wavelength heat energy radiating back from the planet's surface. The result is that increasing levels of CO2 should create a warmer Earth.
Even the most stubborn climate-change skeptics agree (1) our planet is warming alarmingly and (2) CO2 levels are way above their natural range of 180 to 300 ppm over the past half-million years. Few even disagree that the main cause of excess CO2 is our reckless burning of carbon-rich gasoline and coal, combined with deforestation (forests being the planet's largest carbon "sink"). Where they do contest mainstream science is whether the temperature is rising because of increasing CO2 concentration. Perhaps, they argue, the planet is going through a natural warming cycle, meaning that humans are off the hook.
Despite the overwhelming scientific consensus that global warming is indeed human-caused, public opinion in the U.S. barely registers that fact. In 2009, for instance, a Pew survey found that only 49 percent of U.S. residents concur with the statement, "Earth is getting warmer because of human activity," while internationally 79 percent of respondents agree. Is it that we're more inclined than the rest of the world to believe in conspiracy theories? Has Fox News made us dumber? Or is Exxon Mobil's pro-skeptic feel-good advertising campaign just too potent to resist?
Perhaps if we suffered personally from the relentless invasion of the Sahara desert south into the Sahel, or could see for ourselves Greenland's melting ice sheets, or could somehow experience the 40 percent global decline of phytoplankton (the base of the marine food chain) since 1950, we might be more inclined to take notice of overall climate trends. But locally, we see virtually nothing of this, and our local temperatures actually buck the global trend (see bar chart). According to NOAA, the planet has just logged the warmest decade, year, six months, and April, May and June on record; and nine countries recorded their all-time highest temperatures in 2010. Meanwhile, here in Humboldt, the recent trend is cooling!
No surprise here. Warmer air in one place creates more water vapor which leads to increased cloudiness and lower temperatures elsewhere. For instance, most climate change models predict colder, snowier winters for northwestern Europe. Also, we're right next to the vast heat sink of the Pacific. But we're not immune. Eventually we'll start catching up to the rest of the world. Winter storms will be more severe, sea levels will rise, and no longer will we be able to blithely ask, "What global warming?"
Barry Evans (firstname.lastname@example.org) was embarrassed by fellow Brit Freeman Dyson, who recently told Charlie Rose that humans repair the damage they do to the planet.