If we delay decisions on reducing carbon emissions today, it would be the same as handing future generations a bill of $535 trillion, which they would have to pay over the next 80 years. That’s the finding of a new research by James Hansen, a Columbia University professor and former head of NASA’s Goddard Institute for Space Studies.

Professor Hansen estimates that if the world doesn’t treat the reduction of greenhouse gas emissions as a priority today, it would cost as much as $6.7 trillion each year to neutralize the impact of those emissions on the climate. For a comparison, the annual defense budget of all countries together is only about $2 trillion.

At the historic Paris climate change conference in 2015, the 195 participating nations agreed to prevent global temperatures from rising more than 2 degrees Celsius from the pre-industrial level. However, Professor Hansen has proposed a more ambitious target of reducing carbon dioxide levels from the current annual average of 400 parts per million (ppm) to the 1980s levels of 350ppm.

Professor Hansen’s team concludes that the target of 350ppm can be achieved through reforestation, soil improvement, and negative emissions technologies.