It is “extremely likely that humans have been the dominant cause of global warming since the 1950s”

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The Intergovernmental Panel on Climate Change (IPCC) has released its 2013 working group I report which is the 5th assessment report that they have produced.  The report had a total of 209 lead authors and 50 review editors from 39 countries and more than 600 contributing authors from 32 countries.  Collectively these authors conducted a mammoth review of climate research from the last three years. The report, based on scientific evidence, historic records and climate models concludes that it is extremely likely that humans have been the dominant cause of global warming since the 1950’s. Improved models and scientific instrumentation has led to increased certainty of humans influence on the world’s climate since the 4th IPCC report in 2007.

Other key findings include the continued increase in global surface temperature change which is expected to exceed 1.5 °C by the end of the 21st Century, relative to 1850. The oceans are also continuing to warm and the potential absorption of heat by the deep ocean has been offered as one explanation as to why there has been a warming hiatus since 1998.

Levels of carbon dioxide, methane and nitrous oxide have increased by 40% since pre-industrial times.  Changes in land use and increasing usage of fossil fuels are the primary causes for this increase.  The oceans have absorbed 30% of emitted carbon dioxide causing ocean acidification which is only predicted to worsen. Prof Thomas Stocker, a co-chair of the IPCC working group spoke at the conference in the Swedish capital saying that climate change “challenges the two primary resources of humans and ecosystems, and water. In short, it threatens our planet, our only home”.

In this report, scientists conclude that sea level rise will proceed at a faster rate than we have experience over the past 40 years.  It is predicted that waters will rise between 26cm and 82cm depending on the continued levels of greenhouse emissions. The two main factors contributing to sea level rise are the melting glaciers and warming waters, which expand as they heat up.

For the future, the report states that under all models there will be continued warming, and climate change will affect carbon cycle processes in a way that will exacerbate the increase of carbon dioxide in the atmosphere.

The IPCC Summary for Policymakers can be downloaded here

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