The UN’s Intergovernmental Panel on Climate Change (IPCC) released the third part of its massive fifth assessment report (AR5) yesterday.  Building on the science from part I, this section focuses on mitigation – how we can slow down climate change.

Written by 235 scientists from 58 countries, the report finds that quick and dramatic action needs to be taken to avoid a warming increase of 2°C (3.6°F) above pre-industrial levels – a goal set by international agreement.  Driven by population and consumption growth, as stated in the report, “Anthropogenic greenhouse gas (GHG) emissions have increased from 27 to 49 gigatonnes of carbon-dioxide equivalent per year (+80%) between 1970 and 2010; GHG emissions during the last decade of this period were the highest in human history.” While the burning of fossil fuels accounts for the majority of these emissions, deforestation and agriculture also play a key role.

To meet the 2°C target, according to this 2007 Nobel Prize winning group, carbon-dioxide emissions need to be cut by 40%-70% by 2050. And, by 2100, they need to be almost zero. The report emphasizes that delaying mitigation will only increase the cost of dealing with climate change later – both economically and socially.

In writing this tome, experts analyzed over one thousand potential solution scenarios.  While the report does not recommend any one particular policy approach for lowering emissions, it emphasizes that zero-carbon energy sources, like solar, wind, and even nuclear power need to triple by 2050.  It also stresses utilizing carbon capture technology, reforestation, and the implementation of more energy efficient building codes.

According to the report, “Without additional efforts to reduce GHG emissions beyond those in place today … global mean surface temperature increases in 2100 from 3.7°C to 4.8°C (7°F-9°F) compared to pre-industrial levels.” This amount of warming could have catastrophic consequences on human civilization, as pointed out in the IPCC’s Working Group II report on impacts and vulnerabilities released two weeks ago.

This coming autumn, the IPCC will publish an official synthesis of the reports from its three working groups. It will be used as a guide for the policy makers at the next Global Climate Summit scheduled for December 2015 in Paris.  Any treaty agreed to there is supposed to take effect in 2020.