Scientists on the Intergovernmental Panel on Climate Change (IPCC) released their fifth assessment report on global climate change dynamics this month. In addition to reaffirming the assertions of the panel’s four previous assessments with greater statistical accuracy, the new report formally embraces a global upper limit for greenhouse gas emissions, past which the earth would experience irreversible changes to its climate. The models used by the panel are complex and a close eye is required while examining the results. Largely based on the averages of many simulations under many different assumptions, the findings of the panel must be critically analyzed against observational data in order to make useful statements and prescribe actions to mitigate the effects of a warming globe.
Here are some statistical highlights from the 900-page report:
- There is a strong consensus that the complex climate system on our planet is warming. The changes in temperature of the atmosphere and ocean, in the amounts of snow and ice cover, and in the concentrations of greenhouse gases are historically unprecedented.
- The past three decades have experienced higher temperatures at the surface than any other decade since 1850.
- The ocean accounts for over 90% of accumulated energy over the past three decades, resulting in a certain increase in upper ocean temperature.
- Glaciers and ice sheets in Greenland, the Arctic, and Antarctica have consistently lost mass over the past two decades.
- Over the last century, global average sea level has risen by about 0.19 meters. If emissions and subsequent warming continue at their current pace, the average global sea level may rise as much as a meter by the end of the century.
- Greenhouse gases carbon dioxide, methane, and nitrous oxide have reached unprecedented levels in the past 800,000 years. CO2 levels have increased 40% since the preindustrial era, and the ocean has absorbed nearly 30%. The high concentration of CO2 in the ocean results in acidification of the water.
- It can be stated with 95-100% confidence that human activity resulting in the combustion of fossil fuels and the emission of CO2 and other greenhouse gases is responsible for the observed increases in average temperatures.
- Across a range of scenarios, global average temperature may rise anywhere from 1.5oC to 4oC. The models account for decadal and regional variability, which the panel says explains the differences in average temperature projections from the last report.
To keep the magnitude of the warming below the internationally agreed target of 2o C above pre-industrial levels, the panel estimates that roughly 1 trillion tons of CO2 may be emitted into the atmosphere. At the current pace of emission, that threshold would be reached in 2040. The panel’s report fine-tuned the findings of a culmination of over 20 years of research. United Nations Secretary General Ban Ki-Moon has declared his intention to call a meeting of global leaders in 2014 to discuss an international treaty addressing the problem.
In light of this report, the need for President Obama to honor his stated commitment to lead in developing an international approach to adapting to a changing climate is clearer than ever. Developed nations must be held to a higher degree of accountability than developing nations when allocating costs for mitigation strategies. Investment in energy efficiency and clean energy technologies must increase significantly to offset greenhouse gas emissions while meeting global power demand. Education campaigns are essential to prepare populations for the impacts of drought, heavy rain, and rising sea levels as a result of global warming. This report is only the latest installment in a body of research that confirms human influence on the dynamics of the earth’s climate. It lays the framework necessary to begin tackling one of the largest issues of our time, and it didn’t arrive a moment too soon.
This posting was written by Sam Catherman, Green America’s Climate Program Intern.