A few UK scientists have done a smart thing; they’ve combined the proposals of G8 policymakers for combating climate change with actual data on the status of play in the carbon cycle. The resulting study (pdf) is interesting not only because of this highly useful approach but also because it focuses on atmospheric carbon dioxide and its impact on the environment in the far future.
If anything is beyond doubt, it is that making cuts in greenhouse gases won’t be any good if the longer term problem of atmospheric carbon dioxide gets ignored. Atmospheric carbon dioxide threatens to become a massive problem that will catch up with us at a speed way more dangerous than the man made carbon dioxide emission problems we’re facing at the moment, the scientists write in their study, published in the Environmental Research Letters.
The report’s authors warn that long term, atmospheric carbon dioxide will continue to outpace emissions reductions even if the more stringent carbon dioxide emissions reduction targets of 80% are met.The scientists focused on knowledge of what happens to the greenhouse gases once they enter the atmosphere by studying the carbon cycle (the way carbon moves between the oceans, atmosphere and land) to its full extent.
“Gases such as methane or nitrous oxide only remain in the atmosphere for a few years or decades. Carbon dioxide is a different matter as a portion of emitted gas stays in the atmosphere for thousands of years,” said Jo House from the Natural Environment Research Council’s QUEST programme at the University of Bristol, who led the research.
She added that as the climate changes the carbon dioxide that remains in the atmosphere will increase.
“Carbon dioxide is taken up by land and ocean sinks, which become less effective as the climate warms, leading to even greater warming for a given level of emissions – this is known as climate feedback. Our calculations demonstrate the level of emissions reduction we need to achieve to limit climate change to below what is considered ‘dangerous’,” she said.
The scientists say that short-term cuts alone will not solve the problem and that policy makers need to plan for hundreds of years into the future. But they strongly urge that action taken now will have real benefits far into the future. Armed with the latest knowledge of climate change feedbacks relating to the carbon cycle, the scientists ran computer models to see what would happen under the G8 plans to cut global emissions by 50% by 2050. The models show that under this scenario, unless emissions cuts continue beyond 2050, atmospheric carbon dioxide concentrations will continue to rise rapidly.
The same models suggested that by 2100 carbon dioxide concentrations could be as high as 590 parts per million (ppm), far higher than today’s 386ppm. That’s also more than double the level of the millennia before the industrial revolution. And by 2300 the worst-case scenario shows that carbon dioxide levels could be 980ppm, having caused an average rise in global temperature of 5.7°C.
The group of scientists took into account the proposals for emissions reductions by the G8 countries as well as the more stringent proposal of the UK Government’s Stern Review. The Stern Review, which has been largely adopted into the UK government’s policies, proposes to slash emissions by 25% by 2050 and to continue to make cuts down to 80% towards the end of this Century.
When running the Stern data, the models showed a more hopeful future. In this case the carbon dioxide levels would become almost stable, at levels of between 500 and 600ppm by 2100. Yet even these figures would still creep up later in the future if the emissions were not cut back by greater degrees. The Stern Review concluded that, to avoid the worst impacts of climate change, the concentrations of all greenhouse gases should be limited to what is equivalent to between 450 and 550ppm of carbon dioxide concentration.
“To achieve long-term stabilisation of carbon dioxide levels at around 550ppm will require cuts in global emissions of between 81% and 90% by 2300, and even more beyond that time. We applaud the government’s new plans to cut UK emissions by 80% by 2050. This is a realistic assessment of the scale of the problem and the action needed,” says House. “Our research confirms that bringing other countries on board to meet a global target of 80% reductions towards the end of the century will virtually stabilise carbon dioxide levels, but a much longer-term strategy is still needed to reduce future emissions even further.”