Less than a quarter of the proven fossil fuel reserves can be burnt and emitted between now and 2050, if global warming is to be limited to two degrees Celsius (2°C), says a new study published in the journal Nature today.

The study has, for the first time, calculated how much greenhouse gas emissions we can pump into the atmosphere between now and 2050, to have a reasonable chance of keeping warming lower than 2°C (above pre-industrial levels) – a goal supported by more than 100 countries (2). We can only emit 1000 billion tonnes of carbon dioxide (CO2) between the years 2000 and 2050. The world has already emitted one third of that in just nine years.

“If we continue burning fossil fuels as we do, we will have exhausted the carbon budget in merely 20 years, and global warming will go well beyond two degrees,” says Malte Meinshausen, lead author of the study and climate researcher at the Potsdam Institute for Climate Impact Research. The three-year research project involved scientists from Germany, the United Kingdom and Switzerland

The study concluded that greenhouse gas emissions must be cut by more than 50 percent by 2050 relative to 1990 levels, if the risk of exceeding 2°C is to be limited to 25 percent.

“Only a fast switch away from fossil fuels will give us a reasonable chance to avoid considerable warming. We shouldn’t forget that a 2°C global mean warming would take us far beyond the natural temperature variations that life on Earth has experienced since we humans have been around,” says Malte Meinshausen. (Link to full story @ Potsdamn Institute for Climate Impact Research)