Emissions of greenhouse gases grew at a faster rate over the decade from 2000 to 2010 than they did over the previous three decades, reaching the highest levels in human history, despite efforts to limit them, according to the last installment of the latest report from the Intergovernmental Panel on Climate Change (IPCC).
This final installment, focused on mitigating climate change, says that in order to keep warming under the 2°C (3.6°F) threshold agreed upon by the world’s governments at a 2009 meeting in Copenhagen, greenhouse gas emissions in 2050 will have to be 40% to 70% lower than what they were in 2010.
By the end of the century, they will need to be at zero, or could possibly even require taking carbon dioxide out of the atmosphere, which is a controversial proposition.
The scientists who wrote the report examined about 1,000 scenarios for limiting greenhouse gas emissions through combinations of renewable energy development, increased energy efficiency, technologies that would capture and store carbon underground and reforestation efforts.
How to do this while limiting the impact to economic growth and poverty reduction is a key question, and the efforts necessary would likely differ from region to region, country to country, and state to state, the report said.
“The longer we wait, the costlier it will be,” said Charles Kolstad, an environmental economist at the University of California, Santa Barbara, and one of the lead authors of the report.
Half of all the greenhouse gas emissions from humans were emitted within the past 40 years, growing 2.2% per year over the past decade, compared to 0.4% per year over the previous three decades.
This boost has come from two primary sources. “Emissions are increasing along with economic growth and population,” said another lead author, Robert Stavins, a Harvard economics and policy expert.
Climate change has already caused the planet’s average temperature to rise by 1.6°F since the beginning of the 20th century. That temperature rise could reach 2.7°F above pre-industrial levels by the end of the century (and possibly as high as 8.64°F above 1986-2005 levels) if nothing is done to curb emissions, according to the first part of the IPCC’s fifth assessment on climate change, as the entire report is called.
“Things are going to have to change if we do want to control climate change,” said Leon Clarke, an IPCC author and research economist with the Pacific Northwest National Laboratory. “If we do nothing, temperatures will continue to rise.”
Doing something means “de-carbonizing” the global economy, both by reducing the demand for so much energy and by supplying energy that generates far fewer, or no greenhouse gases, the report says. In particular, the use of coal, one of the dirtiest fossil fuels, was a major contributor to the rise in emissions over the past decade with the huge growth of economies like China’s and India’s. Trends like this must be reversed, and if steps aren’t taken to remove carbon from the energy equation, greenhouse gas emissions could double or even triple by the middle of the century, the report says.
One way to de-carbonize energy production is through what IPCC author Benoit Lefevre, of the World Resources Institute, describes as “a fundamental shift in global investment from fossil fuel to renewable energy.” The growth of renewables has been stronger than what was anticipated in the last IPCC report, though emissions increases negated any benefit there, said Bill Hare, a climate scientist who is CEO and managing director of Climate Analytics, a non-profit focused on climate research.
The IPCC doesn’t make specific recommendations on how the switch to renewables should be achieved, though it discusses the direct investment in such technologies, as well as systems like a carbon tax that could push people away from more conventional energy sources.
(April 13, 2014)