An international team of scientists from Austria, France, the UK, Germany and Switzerland concluded that the melting of permafrost and associated carbon emissions reduced the carbon dioxide emissions budget to almost zero. As a result, exceeding the permissible levels of greenhouse gas emissions, which can lead to a climate disaster, is inevitable. The article of scientists was published in the journal Nature Geoscience.
The carbon dioxide emission budget is the amount of carbon dioxide that can be released over a certain period of time, so as not to exceed the level of global warming established by the end of this period. According to the 2015 Paris Agreement, the rise in global average temperature must be capped at 1.5 degrees Celsius to prevent a catastrophic climate change scenario. Researchers have previously estimated that in order to achieve this goal with a 50 percent probability, the budget should not exceed 550 gigatons of CO2. If the current level of emissions is maintained, it will be exhausted in about six years.
Scientists have assessed the impact of carbon dioxide and methane emissions caused by melting permafrost on the emission budget. According to their conclusions, without taking into account the influence of the permafrost zone, the emission of 2320 gigatons of carbon dioxide will exceed the limit of 1.5 degrees Celsius, and the emission of 3230 gigatons will exceed the limit of 2 degrees Celsius. Taking into account the thawing of permafrost, these figures are reduced by 30 and 60 gigatons, respectively. At the same time, the allowable emission budget is reduced even more - by 60 and 100 gigatons, respectively.
There are several scenarios for reaching the limit. Some of them allow a temporary excess of the set values, followed by a decrease in the average temperature. According to the Paris Agreement, the average temperature rise can reach 2.5 degrees Celsius, but then measures must be taken to reduce this value to 2 degrees Celsius. However, in this scenario, the melting of permafrost will lead to a decrease in the emission budget by 16 percent. If the limit is exceeded by one degree, the emission budget will decrease by 25 percent. For the 1.5 degrees Celsius limit, the emission budget is reduced by 10-100 percent.
Thus, exceeding the limits is the most risky strategy, and in a number of scenarios, humanity's emission budget is almost completely exhausted. At present, the scenario of exceeding the limit is being implemented, therefore, scientists conclude, humanity should be prepared for the fact that it will not be possible to return to a safe level of warming.