By Kelly Levin, via WRI Insights.
After a year of extreme weather events and recent studies outlining climate change’s impacts, it’s become increasingly clear that we must understand what emissions reduction pathways are necessary to avoid these risks. The Intergovernmental Panel on Climate Change’s (IPCC) last Assessment Report, for example, outlined the emissions reductions needed from developed countries to stabilize concentrations of greenhouse gases (GHG) consistent with limiting warming to 2°C.
Further research has continued to examine the global GHG emissions reductions necessary to avert dangerous climate change. And as countries implement existing policies and consider new ones, the scale of required emissions cuts is a fundamental question. In fact, it’s one of the most pressing questions facing the international climate change community.
One new study shows that we have to reduce emissions even more than scientists initially thought in order to avoid climate change’s worst impacts. A paper published in Energy Policy on February 20 by Michel den Elzen and colleagues examines new information on likely future emissions trajectories in developing countries. This includes recent clarification of assumptions and conditions related to developing country pledges. In addition, countries have also come forward with further information on their emissions projections. As a result, the report finds that developed countries must reduce their emissions by 50 percent below 1990 levels by 2020 if we are to have a medium chance of limiting warming to 2°C, thus preventing some of climate change’s worst impacts.
This level of reductions is considerably higher than what the scientific community thought was necessary to meet the 2°C goal. The most recent IPCC Fourth Assessment Report laid out a recipe for a medium chance  of limiting warming to 2°C. This report — compiled by the world’s leading climate scientists — stated that developed countries would have to reduce their emissions by 25 to 40 percent below 1990 levels by 2020, and developing country emissions would have to be reduced substantially from their business-as-usual emissions trajectories.
Are We on Track to Achieve These Reductions?
While the den Elzen and colleagues’ paper is just one of many studies on necessary levels of emissions reductions, it lays out a troubling issue: the world may need to reduce its emissions even more significantly than previously thought. The bad news is that we knew we were already far from a 25 to 40 percent reduction in developed countries by 2020. And in light of den Elzen’s new data, we are even further from a 50 percent reduction decline.
In the last few years, both developed and developing countries have come forward with emissions reduction pledges for 2020, and several initiatives have assessed whether meeting these pledges would achieve the level of ambition required. For example, an early WRI analysis found that emissions reductions from developed country pledges added up to only 12 to 18 percent below 1990 levels by 2020. We have since participated in the U.N. Environment Programme’s Emissions Gap Report, which has found the gap between current pledges and what’s needed to limit warming to 2°C to be between 8 and 13 gigatonnes of CO2 equivalent. (For context, in 2005, emissions from the world’s cars, buses, and trucks were roughly 5 gigatonnes.) It is clear that the world is currently not on course to limit warming below 2°C unless it changes its energy and land use policies dramatically and quickly.
Meeting the 2 Degree Goal Will Require Ambitious and Immediate Action
The findings from this most recent study suggest that the challenge we already knew was great is even more difficult. But even with an increased level of reductions necessary, the study does show that a 2°C goal is still attainable — if we act ambitiously and immediately.
The early seeds of transformation we are seeing in Europe, the United States, and some developing countries need to be scaled up quickly (WRI recently laid out several policy recommendations for the United States to significantly reduce its greenhouse gas emissions). At the same time, we need further financing and technology transfer to bend developing countries’ emissions trajectories. Equally important is for the international community to work together to identify additional opportunities for raising ambition. The UNFCCC negotiations have started a dialogue on this, but these conversations need to lead to action. WRI has outlined how “international clubs” could make a difference.
This research demonstrates that now more than ever, leaders must understand the risk of inaction and put in place ambitious, effective policies to build a low-carbon economy. The gap between current and necessary ambition is growing, as is the urgency of addressing global climate change.
 A 450 ppm CO2e goal is associated with a 26 to 78 percent risk of overshooting a 2ºC goal (Meinshausen 2005).
-– This piece was originally published at WRI Insights and was reprinted with permission.