Disputes between leaders of rich and poor countries currently mean little comes from meetings where they’re meant to draw up plans to slow and stop climate change. But developed countries’ existing promises would achieve just 1/3 of any warming slowdown, even though we’re responsible for more than 2/3 of CO2 emissions before 2005. That’s according to a team of mainly Chinese researchers who have tried to settle these fights using “earth system” models, considering both natural and human factors. “Developed countries need to take more responsibility in climate mitigation by cutting more carbon emissions and helping developing countries to control carbon emission while maintaining economic development,” said Xuefeng Cui from Beijing Normal University (BNU).
At the United Nations’ Climate Change Conference in Cancún, Mexico, in November 2010, leaders agreed to try and limit the global temperature rise to 2°C higher than pre-industrial levels. They also agreed that doing this needs deep, but fair, cuts in the amount of warming-causing greenhouse gases humans emit. But they still argue about how to share those cuts. That prompted Cui and his team to make an unusual effort to use science to show what is fair. “The arguments in the IPCC process demand some fact-based reasoning rather than just the ‘blame game’,” team member John Moore told Simple Climate. “Our study is the first interdisciplinary study by climate, social, economic, and ecological scientists and policy makers to look at the historical responsibilities and effect of future mitigation by applying state-of-art earth system models,” Xuefeng added.
Getting such a broad view meant that the team had to develop entirely new methods for their research, published online in the scientific journal Proceedings of the National Academy of Sciences of the USA on Monday. “Most scientists are interested in the real impacts rather than assigning responsibilities,” Moore said. “These are more abstract philosophical and moral points than they tend to consider.” It took a 37-strong team of scientists to develop the approach, and one of the two earth systems models, they used. Whole earth system models are needed to understand the effects plants, animals, land and oceans have on climate.
Picture of the past
Though there are records of CO2 emissions from the past, they’re not broken down by country, meaning the models John and Xuefeng’s team used also had to work that out. The scientists were quick to point out what this meant about how their results should and shouldn’t be seen. “The projections should not be regarded as precise predictions,” Xuefeng said. However, the models have a solid scientific foundation and can provide detailed insights into the climate system, he added. “Our models can help answer the complicated climate attribution and mitigation questions.”
To do this, the researchers ran three experiments on each of the earth system models. One included CO2 emitted by all countries, one only CO2 from richer countries, and the last CO2 from developing countries. They also looked at different ways we could emit CO2 in future. These included “business as usual”, or rich countries only staying within their promised limits, or poor countries only emitting as promised, or all countries sticking to their promises. The Chinese team’s model projected more than 3°C warming between 1850 and 2100 if everyone stuck to their promises, and more than 4°C if no-one did. The other model, developed in the US, projected 2°C warming by 2100 for the lowest CO2 emission case and more than 3°C for the highest. But both models showed similar shares of past emissions and future temperature rise between when rich and poor countries deliver on their promises.
“Developed countries contributed 2/3 of historical greenhouse gases emissions and current climate warming since pre-industrialization,” John said. “Even though developing countries presently emit more CO2, they started later. The current political pledges made by developed countries will only contribute 1/3 of climate remediation even if they follow all of them. Therefore the developed world is avoiding responsibility for both the past and future climate change and morally should do more. But so should developing countries since serious measures are needed to prevent dangerous climate change. All countries need to make serious reductions in CO2 emissions. Our results provide a moral and scientific frame for climate negotiations. ”
The suspicious might think that this finding is what you’d expect from a largely Chinese group – but John and Xuefeng listed reasons that they’ve been as neutral as scientists should be. Among them is the fact that their new model works by bringing together existing models, many of which came from the US. “Our work is funded by China,” John said. “We work with many international groups, the article was peer-reviewed by non-Chinese, and the results will be included in the new IPCC report which has models from many countries. The results can be easily checked with any of these models in other labs. The fact that the US models and the BNU model gave such similar results suggests that the findings are robust.”
The scientists will now go on to add more detail to their models – in particular the effect of aerosols, fine solid or liquid particles like dust and soot, and which countries produce them. They’ll also look at what geoengineering methods to cool the planet without reducing CO2 emissions might do. Xuefeng also said they’d like to see other researchers do similar studies, and would like to co-operate with them. “We would recommend other climate model groups perform such experiments to provide higher confidence in the historical responsibilities and more importantly the effects of climate mitigations,” he said.