In the last two weeks, reporters have repeated false numbers provided by a study and a report (and by their respective press releases) related to the banding of penguins and global warming’s impact on global food production (the ever-vigilant Knight Science Journalism Tracker covered both episodes).
Most recently, an Argentina-based NGO, Universal Ecological Fund, released a report describing how climate change will affect food production in various parts of the world. One of its key findings was that the concentration of greenhouse gases in the atmosphere would rise to 490 parts per million (ppm) of CO2-equivalent (a unit of measure aggregating all such gases) by 2020, corresponding to a 2.4-degrees Celsius rise in temperature.
EurekAlert!, the widely used news service run by the American Association for the Advancement of Science (AAAS), issued a press release from the NGO touting the report, which was covered by numerous news outlets worldwide. The claims about the rise in CO2-equivalent and temperature were patently false, however.
Guardian environment correspondent Suzanne Goldenberg was among the few reporters to catch the gaffe. Sensing that something was amiss, she e-mailed NASA climate modeler Gavin Schmidt, who wrote back: “2.4C by 2020 (which is 1.4C in the next 10 years - something like six to seven times the projected rate of warming) has no basis in fact.”
Schmidt followed up with a post at RealClimate.org, a blog he runs with some of his fellow climatologists, which explained exactly where Universal Ecological Fund went wrong, and it’s worth quoting at length. The NGO made two basic mistakes:
The first error is in misunderstanding what CO2-eq means and is used for. Unfortunately, there are two mutually inconsistent definitions out there (and they have been confused before). The first, used by policymakers in relation to the Kyoto protocol, relates the radiative impact of all the well-mixed greenhouse gases (i.e. CO2, CH4, N2O, CFCs) to an equivalent amount of CO2 for purposes of accounting across the basket of gases. Current GHG amounts under this definition are ~460 ppm, and conceivably could be 490 ppm by 2020.
However, the other definition is used when describing the total net forcing on the climate system. In that case, it is not just the Kyoto gases that must be included but also ozone, black carbon, sulfates, land use, nitrates etc. Coincidentally, all of the extra GHGs and aerosols actually cancel out to a large extent and so the CO2-eq in this sense is quite close to the actual value of CO2 all on its own (i.e. in IPCC 2007, the radiative forcing from CO2 was 1.7 W/m2, and the net radiative forcing was also 1.7 W/m2 (with larger uncertainties of course), implying the CO2-eq was equal to actual CO2 concentrations).
In deciding how the climate is going to react, one obviously needs to be using the second definition. Using the first is equivalent to assuming that between now and 2020 all anthropogenic aerosols, ozone and land use changes will go to zero. So, they used an excessive forcing value (3 W/m2 instead of ~2 W/m2).
The second mistake
has a bigger consequence:is that they assumed that the instantaneous response to a forcing is the same as the long-term equilibrium response. This would be equivalent to a planet in which there was no thermal inertia - or one in which there were no oceans. Oceans have such a large heat capacity that it takes decades to hundreds of years for them to equilibrate to a new forcing. To quantify this, modelers often talk about transient climate sensitivity, a measure of a near term temperature response to an increasing amount of CO2, and which is often less than half of the standard climate sensitivity.
Goldenberg brought Universal Ecological Fund’s error to the attention of EurekaAlert!, which quickly removed the related press release from its website.
“We primarily rely on the submitting organization to ensure the veracity of the scientific content of the news release,” Ginger Pinholster, the director of AAAS’s communications office, told her.