Posts Tagged ‘Quaternary’


CO2 hits 390 ppm

16 May 2010

The level of carbon dioxide (CO2) in the atmosphere, as measured at Mauna Loa, has just ticked over to 390 ppm.

Actually, that’s not quite true — the level is 392.39 ppm as of April. But CO2 levels are slightly higher during the northern spring than the southern spring, because the Northern Hemisphere has more land and hence more vegetation breathing out CO2. Once you adjust for this seasonal cycle, then the current CO2 level is 389.64 ppm — which rounds to 390.

I first got interested in global warming about four years ago when I read TIME magazine’s special issue on global warming. At that time, the CO2 level (again, seasonally adjusted) was around 382 ppm. It reached 383 ppm by December 2006, 384 ppm by April 2007, 385 ppm by November 2007, 386 ppm by June 2008, 387 ppm by January 2009, 388 ppm by August, 389 ppm this February, and now 390 ppm. All these numbers come from measurements made at Mauna Loa observatory, but wherever you look you’ll get similar results.

CO2 at Mauna Loa since 2006. (Source: Earth System Research Laboratory)

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Global Warming Contrarians Part 5: Counting Carbon

27 March 2010

This is the latest instalment in a continuing series of posts on the (mostly bad) arguments that contrarians make against global warming. A list of earlier parts in the series can be found at the bottom of this post.

Claim: Natural CO2 emissions far outweigh our own.

Fact: This claim is true but misleading. Before the Industrial Revolution, natural emissions of 698 Gt/yr were balanced by natural absorptions of 698 Gt/yr (neglecting volcanic emissions, which make no significant difference on human timescales):

Average CO2 emissions and absorptions circa 1750. All figures are in gigatonnes of CO2 (GtCO2); to convert to gigatonnes of carbon (GtC), multiply by 3/11. (Simplified version of IPCC AR4 WGI Figure 7.3)

Human emissions are indeed much lower than natural emissions (for 2000-2008, 28.1 Gt/yr from fossil fuels and 5.3 Gt/yr from land use change), but they are not balanced by natural absorption, so the CO2 has been building up in the atmosphere: Read the rest of this entry ?


Global Warming Contrarians Part 4: Back to Basics

23 March 2010

So far in my series of posts on the arguments contrarians make against global warming, I’ve written about the changes being observed in the Earth’s climate. I wrote about whether the global temperature has increased (short answer: yes); whether it has recently stopped increasing (short answer: probably not); and whether ice is declining around the world (short answer: yes). Now I figure it’s time to go back to where it all begins: with CO2 and the greenhouse effect.

Claim: The greenhouse effect does not exist.

Fact: The greenhouse effect is as established a phenomenon as any. It was first discovered in the 1820s by French mathematician Joseph Fourier, and the basic physics was essentially understood by the 1950s. Greenhouse gases are completely transparent to visible light but less so to infrared. Visible sunlight is transmitted through the Earth’s atmosphere and warms the surface, causing Earth to emit infrared light (because Earth is much cooler than the Sun, its radiation peaks at a lower wavelength). But on the way out, some of this radiation is trapped by greenhouse gases, which reflect it back to Earth and make the surface warmer. If it were not for the greenhouse effect, the Earth’s average surface temperature would be about 33°C colder.

Claim: CO2 is not evil/not a pollutant.

Fact: The “straw person” fallacy is committed when one (intentionally or otherwise) misrepresents the argument one is attempting to counter. “CO2 is not evil” could be a textbook example. Of course there is nothing inherently evil about carbon dioxide — but nobody is claiming that there is. It’s just another molecule. Read the rest of this entry ?