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Sobering news on the state of Earth's climate: Report

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By Gina Ressler
Meteorologist
@ginaressler
Monday, September 30, 2013, 8:24 AM

The scientific community was abuzz on Friday, following the release of the latest climate assessment report from the Intergovernmental Panel on Climate Change (IPCC).

The report contained some sobering news about the state of the earth’s climate, and drove home some key points that climate scientists have been talking about for years. The report states that since the 1950s, “the atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and concentrations of greenhouse gases have increased.”

And according to the report, we’re more certain than ever that human activity has been the dominant cause. 

But climate studies are published all the time.  What makes the IPCC report so important?  Here’s a quick background: 

What is the IPCC?

The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO), and is considered the leading international body for the assessment of climate change. Thousands of scientists from around the world contribute to the work of the IPCC.   

What an IPCC Assessment Report?

Every five or six years, the IPCC releases a massive report summarizing the current state of knowledge on climate change.  To put together the report, the IPCC reviews thousands of sources of scientific and technical information, with priority given to peer-reviewed literature.  The review process includes worldwide participation, with hundreds of experts reviewing the accuracy and completeness of the science.  In short, an IPCC report isn’t just one study -- it’s a summary of thousands of studies.  It’s considered to be the most comprehensive and authoritative source of climate information in the world. The previous Assessment Report was released in 2007, for which it earned a Nobel Peace Prize. 

This week in Stockholm, the IPCC released the first part of its Fifth Assessment Report, called the “Summary for Policymakers.” The remaining sections (thousands of pages in total) will be released in stages over the next 12 months.  

Here are some of the key points outlined in the report:

  • Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.
  • Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983-2012 was likely the warmest 30-year period of the last 1400 years. 
  • Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent.
  • The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia. Over the period 1901-2010, global mean sea level rose by 0.19 m.
  • The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years.
  • Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence has grown since the Forth Assessment Report. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. 

Image: IPCC

Image: IPCC

Is climate change linked to more extreme weather events?

This issue is more complex.  The report notes that some types of weather extremes have shown a clear trend over the past few decades. The number of warm days and nights has increased, for example, while the number of cold days and nights has decreased.  The frequency of heat waves and heavy precipitation events also appears to have increased in some parts of the world.  But no clear trend has been shown for hurricanes, although this remains an area of active research. 

The goal of the IPCC Assessment Report is to act as a guide to governments and policy-makers. 

The report can be found here.

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