Greenhouse gas emissions are growing but limiting warming remains possible

The Intergovernmental Panel on Climate Change (IPCC) has released the “Fifth Assessment Working Group 3 report” which documents recent trends in greenhouse gas emissions and identifies their sources. It assesses options for reducing emissions of these gases to limit future human- induced changes in climate.

A media release from NIWA sums up the report, saying it shows that global greenhouse gas emissions have continued to grow, on average at 2.2% a year between 2000 and 2010. Carbon dioxide remains the major long-lived greenhouse gas emitted as a result of human activities.

Economic growth and population growth are the two main drivers of recent increases in global carbon dioxide emissions from fossil fuel combustion. They outpaced gains from producing and using energy more efficiently.

The report considers a wide range of potential scenarios for future greenhouse gas emissions, and concludes that scenarios that limit CO2-equivalent concentrations in 2100 to about 450 parts per million are likely to keep global temperature change below 2°C. It says such scenarios include substantial cuts in anthropogenic greenhouse gas emissions by mid-century.s).

The report says that without additional efforts to reduce greenhouse gas emissions,emissions growth is expected to persist. But it also identifies and assesses measures and technologies that could assist with reducing emissions. Potential improvements are available through low-carbon energy generation, more energy-efficient transport, buildings and industry, reduced deforestation, bioenergy, better management of cropland and grazing land, and urban planning affecting infrastructure, land use and transport choices.

Dr David Wratt of the NZ Climate Change Centre and NIWA has attended the plenary meetings of all three IPCC Working Groups.

He says:

“The first two reports of the IPCC Fifth Assessment confirm that climate change poses major problems. This third report shows that our actions to date are not enough to put us on a global track for limiting warming to 2 degrees. But the report also provides options for reducing emissions – and shows that if we make sufficient reductions we can escape some of the more serious impacts that would result from unconstrained climate change”.

Full text of the “Summary for Policymakers” of the IPCC Working Group 3 Report will be available on the IPCC website.

Three New Zealand experts contributed substantially to the report: Professor Ralph Sims of Massey University as a Convening Lead Author of the chapter on Transport, Dr Harry Clark, Director of the New Zealand Agricultural Greenhouse Gas Research Centre as a Lead Author of the chapter on Agriculture, Forestry and Other Land Uses, and Dr Adam Jaffe Director of Motu Economic & Public Policy Research as a Lead Author of the chapter on National and Sub-National Policies.

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