The amount of CO2 that can be released into the atmosphere before it is too late is half of what was previously thought. So fossil fuels must be phased out at twice the speed. The Paris Agreement was too optimistic.
Climate scientists have some bad news for governments and energy sector businesses: to keep global warming within the limits established by the international community at last December's Paris conference, the use of fossil fuels will need to be reduced at an even faster pace — at least twice as fast as the agreements envisage.
Joeri Rogelj, a researcher at the Austrian International Institute for Applied Systems Analysis, together with his European and Canadian colleagues, has published a study in Nature Climate Change arguing that all previous estimates of the quantity of carbon dioxide released into the atmosphere have in fact been too generous, and that the levels identified as potentially catastrophic for the environment could be reached far sooner than expected. Indeed, the Earth's carbon budget — that is, the balance indicating how much CO2 we can still emit into the atmosphere without breaching the threshold of a 2 degree Celsius rise in global temperature — is half of what has been estimated to date. This means that instead of 2,390 billion tonnes of CO2, our atmosphere will be able to absorb 1,240 billion tonnes — roughly half — before the effects become irreversible.
Since the Industrial Revolution, global temperature has risen by 1 degree and sea levels by 14 centimetres. In 2014, CO2 emissions amounted to just under 36 billion tonnes. According to the calculations in Rogelj's study, at this rate the available carbon budget will be exhausted within 34 years. This means that from 2050 onwards all the world's states would need to be at zero emissions to prevent the Earth's thermometer from rising by more than 2 degrees. "The global CO2 balance is really the equilibrium between what animals and human beings emit and how much plants and algae are able to absorb," Rogelj adds. "It is very important to know this balance because only then can we define the quantity of carbon dioxide we are permitted to release into the atmosphere."
But there is no shortage of good news. Looking at the data published by Global Carbon Project, 2015 was the first year to show a decrease in CO2 emissions into the atmosphere: minus 0.6 per cent compared to 2014. It had not been seen since 2009 that such a reversal of course had occurred. Experts associate this with the growing shift — especially in the most industrialised countries — from fossil fuel energy plants to clean and renewable energy plants. The trend is therefore pointing in the right direction but, as noted at the outset, this process needs to be accelerated so that the available carbon budget is not depleted in too short a time.