You could be forgiven for not fully understanding what’s what with the forthcoming UN-sponsored climate summit in Copenhagen, popularly unknown as “COP15”. Lobbying from all parties in the weeks leading up to the meeting has been fast and furious, politicians are sending out confused and contradictory messages, and journalists struggling to keep up with developments.
For a concise introduction to the key points and processes of COP15, you would do well to read a four page briefing provided by the International Institute for Environment and Development.
Yesterday, a political hand grenade was thrown into the mix. In a paper published in the journal Nature Geoscience, Norwich-based climate scientist Corinne Le Quéré and her colleagues point out that fossil fuel emissions of carbon dioxide rose by nearly a third between 2000 and 2008. Much of this dramatic increase can be attributed to economic growth in developing countries, including China – a growth driven in part by consumer demand in the west.
Reporting of Le Quéré et al.’s work in the mass media focuses on the level of warming we can expect if carbon emissions are not radically curtailed. Two degrees is now so twentieth century. In fact, six degrees is quoted by the BBC’s Richard Black, referring to notes of a discussion with Le Quéré. It’s not a figure set out in the research paper, and for good reason. The main question there concerns uncertainties in the ability of the world’s carbon sinks to cope with the greenhouse gases we are increasingly spewing into the atmosphere.
Six degrees should for the moment not be taken too seriously. As the Met Office head of climate impacts and IPCC member Richard Betts says, such a large degree of warming is but one of a number of possible scenarios, all of which depend on the mitigation strategies pursued…
“Year-to-year changes in the global economy have quite an effect, and it’s too early to discern longer term, robust changes. However, if we continue to let emissions rise without mitigation, there’s a strong chance we’ll hit 4C and beyond.”
Quoting now from Le Quéré et al.’s Nature Geoscience paper…
“Progress has been made in monitoring the trends in the carbon cycle and understanding their drivers. However, major gaps remain, particularly in our ability to link anthropogenic CO2 emissions to atmospheric CO2 concentration on a year-to-year basis; this creates a multi-year delay and adds uncertainty to our capacity to quantify the effectiveness of climate mitigation policies.”
Climate scientists such as Le Quéré say that in order to fill this gap, the residual carbon dioxide flux – i.e., sources minus sinks – from the sum of all known components to the global carbon budget needs to be dramatically reduced. Improvements in climate models and observing systems could provide much needed numerical constraints on global carbon dioxide emission estimates.
The authors go on to say that the recent trend in the airborne fraction of total carbon emissions suggests that the observed growth in the ability of the Earth system to absorb this extra carbon is failing to keep up with the increase in greenhouse gas emissions. Model results indicate that the trend could be due to the response of land and ocean sinks to climate variability and change…
“If the model response to recent changes in climate is correct, this would lend support to the positive feedback between climate and the carbon cycle that was predicted by many coupled climate–carbon cycle models. However, these models do not yet include many processes and reservoirs that may be important, such as peat, buried carbon in permafrost soils, wild fires, ocean eddies and the response of marine ecosystems to ocean acidification. An improved knowledge of regional trends would help to constrain the climate–carbon cycle feedback better.”
Le Quéré and her colleagues conclude their scientific study with a most apposite comment on environmental economics. The authors say that the key to sustained carbon emissions reductions lies in restructuring primary energy use to decouple emissions from GDP.
My guess is that if we don’t do this, then we are well and truly buggered. The ability of the human species to solve such serious environmental problems depends on awareness and will as much as technical ingenuity. When it comes to the current bunch of world leaders and industrialists, however, my impression is one of sensorily-challenged primates frightened into inaction.
Mike Shanahan, “COP15 for journalists: a guide to the UN climate change summit”, IIED (November 2009)
Le Quéré et al., “Trends in the sources and sinks of carbon dioxide”, Nature Geoscience (2009)