There is new support for the rejection of the IPCC focus on CO2 as the primary human climate forcing.
In my weblog of May 2 2008 titled
The climate issue, with respect to how humans are influencing the climate system, can be segmented into three distinct hypotheses. These are:
- The human influence is minimal and natural variations dominate climate variations on all time scale;
- While natural variations are important, the human influence is significant and involves a diverse range of first-order climate forcings (including, but not limited to the human input of CO2);
- The human influence is dominated by the emissions into the atmosphere of greenhouse gases, particularly carbon dioxide.
The third hypothesis, of course, is the IPCC perspective.”
Only one of these hypotheses can be true.
There is a news release by Lauren Morello for the E&E Publishing Service on a paper appearing in the Proceedings of the National Academy of Science [PNAS] that is headlined “Don’t forget the other GHGs, scientists say”.
Extracts from the news article include
“When it comes to climate change, carbon dioxide isn’t the only target……While reducing the world’s carbon dioxide output is important, Molina and his co-authors [of the PNAS study] say other steps are necessary to reduce the risk of tipping points such as the disappearance of Arctic summer sea ice, melting of the Greenland and West Antarctic ice sheets, and dieback of the Amazon rainforest. The strategies include using the existing Montreal Protocol — which governs chemicals that deplete the ozone layer — to end use of hydrofluorocarbons. Known as HFCs, the chemical refrigerants harm ozone and trap heat up 100 to 12,000 times more effectively than CO2…… In addition to cutting HFCs, the PNAS analysis suggests slashing emissions of black carbon (sooty particles produced by diesel engines)……..One recent study estimated that black carbon emissions caused half the total warming in the Arctic between 1890 and 2007 …..Other steps the new paper outlines include slowing the rate of deforestation and reducing emissions of carbon monoxide, nitrogen oxides, methane and other volatile organic compounds that react with sunlight to form tropospheric ozone, “a major pollutant and significant GHG.”
The PNAS article is
M. Molina et al., PNAS, Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions. Proceedings of the National Academy of Sciences, published online before print October 12, 2009; doi: 10.1073/pnas.0902568106
The abstract reads
“Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into abrupt change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of “dangerous anthropogenic interference” (DAI). Scientific and policy literature refers to the need for “early,” “urgent,” “rapid,” and “fast-action” mitigation to help avoid DAI and abrupt climate changes. We define “fast-action” to include regulatory measures that can begin within 2–3 years, be substantially implemented in 5–10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO2 GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global warming potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of abrupt climate change in the next few decades by complementing cuts in CO2 emissions.”
While this PNAS article is still perpetuating (incorrectly) the dominance of the human input of CO2 as the primary climate forcing, as well as the flawed climate science concept of a “tipping point”, the news reported is quite perceptive. Reading the excellent news article, the message of the PNAS paper is really quite broader than that presented by the IPCC.
This news story and the associated PNAS article provide further reasons to reject the narrow IPCC viewpoint as represented by the third hypothesis listed above, since a range of other climate forcings are recognized as being first order climate forcings. In terms of positive radiative forcings, I reported on this topic in
Pielke, R.A. Sr., 2006: Regional and Global Climate Forcings. Presented at the Conference on the Earth’s Radiative Energy Budget Related to SORCE, San Juan Islands, Washington, September 20-22, 2006
where I concluded (see slide 10) that instead of the 48% of human caused warming from CO2 as given by the IPCC, only about 26.5% (see slide 12) is due to the human addition of CO2. It is the second hypothesis
“While natural variations are important, the human influence is significant and involves a diverse range of first-order climate forcings (including, but not limited to the human input of CO2)”
which is supported by the science of the climate system.