You may have heard that the release of greenhouse gases has recently gone down, to match levels of several years ago. Why, then, do we have someone saying that greenhouse gasses have reached a new record high?

There are two, maybe three, reasons.

First, even though CO2 release from the US may be lower now than it has been in a few years, it is still high (it was high a few years ago, so we've reduced to a level that is high!). More importantly, the US has reduced its release of CO2 primarily for incidental economic reasons. With a recession/depression going on, there is less money being spent on things that burn fuel. But, we are also producing more fossil carbon-containing products that we send to other countries, where that fuel is burned, thus releasing the CO2. So, globally, CO2 release is probably as high as it has ever been, more or less.

Second, the greenhouse gasses stay in the atmosphere for a long time. Releasing less does not make what is there go away, really. So if we add less for a couple of years, we still increase the amount.

Third, and less understood, and perhaps not even part of the current calculation of greenhouse gas release, is the extra methane that is being released at large but as yet understudied quantities from drilling operations including those that involve fracking.

So, with those caveats, we have this report from the UN's World Meteorological Organization:

Greenhouse Gas Concentrations Reach New Record: WMO Bulletin highlights pivotal role of carbon sinks Geneva, 20 November (WMO) – The amount of greenhouse gases in the atmosphere reached a new record high in 2011, according to the World Meteorological Organization. Between 1990 and 2011 there was a 30% increase in radiative forcing – the warming effect on our climate – because of carbon dioxide (CO2) and other heat-trapping long-lived gases.

At this point I would like to pause and note something important. Here we learn that there has been a 30% increase in warming effects from 1990 onward. This does not mean, however, that Anthropogenic Global Warming (AGW) started in 1990. You will often see Climate Science Denialists refer to events earlier in the last 100 years as evidence that global warming is not real. If global warming supposedly causes large storms, and there was a large storm in the 1930s, or if global warming supposedly causes droughts, and there was the Dust Bowl in the 1930s, then global warming is not real, the story goes. However, global warming is largely the result of the release of Carbon from the burning of coal and petroleum, and that (especially the coal) started way back in the 18th century and really took off in the mid 19th century. Global warming and its effects have certainly been much more significant over the last several decades, but the effects are much older than that. To return to the UN report...

Since the start of the industrial era in 1750, about 375 billion tonnes of carbon have been released into the atmosphere as CO2, primarily from fossil fuel combustion, according to WMO’s 2011 Greenhouse Gas Bulletin, which had a special focus on the carbon cycle. About half of this carbon dioxide remains in the atmosphere, with the rest being absorbed by the oceans and terrestrial biosphere. “These billions of tonnes of additional carbon dioxide in our atmosphere will remain there for centuries, causing our planet to warm further and impacting on all aspects of life on earth,” said WMO Secretary-General Michel Jarraud. “Future emissions will only compound the situation.” “Until now, carbon sinks have absorbed nearly half of the carbon dioxide humans emitted in the atmosphere, but this will not necessarily continue in the future. We have already seen that the oceans are becoming more acidic as a result of the carbon dioxide uptake, with potential repercussions for the underwater food chain and coral reefs. There are many additional interactions between greenhouse gases, Earth’s biosphere and oceans, and we need to boost our monitoring capability and scientific knowledge in order to better understand these,” said Mr Jarraud.

“WMO’s Global Atmosphere Watch network, spanning more than 50 countries, provides accurate measurements which form the basis of our understanding of greenhouse gas concentrations, including their many sources, sinks and chemical transformations in the atmosphere,” said Mr Jarraud. The role of carbon sinks is pivotal in the overall carbon equation. If the extra CO2 emitted is stored in reservoirs such as the deep oceans, it could be trapped for hundreds or even thousands of years. By contrast, new forests retain carbon for a much shorter time span.

The Greenhouse Gas Bulletin reports on atmospheric concentrations – and not emissions - of greenhouse gases. Emissions represent what goes into the atmosphere. Concentrations represent what remains in the atmosphere after the complex system of interactions between the atmosphere, biosphere and the oceans. CO2 is the most important of the long-lived greenhouse gases – so named because they trap radiation within the Earth’s atmosphere causing it to warm. Human activities, such as fossil fuel burning and land use change (for instance, tropical deforestation), are the main sources of the anthropogenic carbon dioxide in the atmosphere. The other main long-lived greenhouse gases are methane and nitrous oxide. Increasing concentrations of the greenhouse gases in the atmosphere are drivers of climate change. The National Oceanic and Atmospheric Administration’s Annual Greenhouse Gas Index, quoted in the bulletin, shows that from 1990 to 2011, radiative forcing by long-lived greenhouse gases increased by 30%, with CO2 accounting for about 80% of this increase. Total radiative forcing of all long-lived greenhouse gases was the CO2 equivalent of 473 parts per million in 2011.

The report goes on to state that CO2 is the single most important human generated greenhouse gas, but also discusses methane, which I mentioned above, and discusses Nitrous oxide as well.

(Thanks to Brad Johnson for the info on hydrocarbon exports.)