On Sept. 23, the United Nations Climate Summit was held in New York. Many world leaders, including President Barack Obama, attended. In the days just before the summit, the 2014 Global Carbon Budget was published in detail, giving the world leaders access to data on atmospheric carbon. Illinois atmospheric sciences professor Atul Jain was among the many scientists worldwide who contributed data to the report. Jain talked about the carbon budget and the climate summit with News Bureau physical sciences editor Liz Ahlberg.
What is a "global carbon budget"? How is the budget set?
The global carbon budget determines accurate assessments of anthropogenic (man-made) carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere. A budget estimate is important to better understand the global carbon cycle, support the climate policy process and project future climate change.
Present-day analysis of the carbon budget requires the combination of a range of data, algorithms, statistics and model estimates of carbon stocks and fluxes and their interpretation by a broad scientific community.
What increases did the 2014 carbon budget reveal, and how do carbon emissions now compare to historical benchmarks?
The 2014 Carbon Budget report shows that carbon dioxide emissions, the main contributor to global warming, are set to rise again in 2014 - reaching a record high of 40 billion tons. The largest emitters were China, the U.S., the EU, and India, together accounting for 58 percent of the global emissions in 2013. The atmospheric CO2 growth of 2.54 parts per million (19.8 billion tons of CO2) was high in 2013, reflecting the increase in fossil emissions, and smaller changes between the ocean and land carbon sinks compared to the past decade.
Looking at historic trends, fossil fuel emissions in the last 10 years grew an average of 2.5 percent per year, lower than the growth rate in the 2000s (3.3 percent) but higher than the growth rate in the 1990s (1 percent). The declining growth rate in recent years is associated with lower gross domestic product (GDP) growth compared to the 2000s, particularly in China.
Who prepared the 2014 report? What data did you contribute?
The Global Carbon Project's report each year incorporates data from multiple research institutes around the world on CO2 emissions, carbon increases in the atmosphere, and land and ocean sinks for its annual assessment of the Earth's carbon budget. The "Global Carbon Budget 2014," led by Corinne Le Quéré, the director of the Tyndall Centre at the University of East Anglia, has 59 co-authors from 10 countries and 49 institutions. It is published in the "living data" format to provide the highest transparency and traceability in the reporting of this set of key indicators and drivers of climate change.
I contributed our earth system model - the Integrated Science Assessment Model - which estimates global land use change, CO2 emissions and the terrestrial residual sink, and provides a consistent assessment of the causes of carbon fluxes on land.
What does the report suggest about future projections of CO2 emission? Are there ways to control those emissions?
Fossil fuel emissions for 2013 are at the high end of emissions scenarios used by the Intergovernmental Panel on Climate Change to project climate change, as a result of continued GDP growth. Given current projections of the world GDP, emissions are expected to grow further in the absence of more stringent mitigation.
The study shows that the increasing trend of CO2 emissions over the past decades is continuing, despite discussions to limit climate change. The study also suggests that in order to limit the temperature increase to two degrees Celsius, a target that researchers believe may limit the worst effects of climate change, future cumulative emissions would need to be limited to no more than 1200 billion tons of CO2. At the 2014 emissions level, this quantity of emissions would be reached in 30 years. But if emissions continue to rise as projected, this limit would be reached sooner.
What do you hope to see come out of the UN Climate Summit?
At the 2009 Copenhagen meeting, world leaders reached a nonbinding agreement to limit global warming to two degrees Celsius over the pre-industrial average, but they have yet to agree on tougher emissions targets and how the cuts will be shared between nations. This report has come ahead of the United Nations Climate Summit, which I hope will lead to a global agreement in 2015 to cut carbon emissions and fight climate change.