Wendell Tangborn / The Guardian – 2015-10-01 01:57:58

http://www.theguardian.com/commentisfree/2015/sep/28/glacier-melt-climate-change-tipping-point

Glacier Melt Shows a Climate Change Tipping Point. We Must Pay Attention
Wendell Tangborn / The Guardian

(September 28, 2015) — Mountain glaciers and humans have coexisted for roughly 200,000 years, but that long idyll appears to be ending. The earth’s 190,000 glaciers, sentinels of climate change that appear to be more sensitive to the climate than are humans, are disappearing at an unprecedented pace, the canaries in climate change’s coal mine.

It is all being driven by human activities, and it has been happening for three decades. The fate of both humans and glaciers will depend on drastically reducing carbon dioxide emissions during the next decade.

Most of the world’s glaciers began changing in the late 1980s from relative stability to negative mass balances. Mass balance is the difference between growth from snow accumulation and shrinkage from snow and ice melting.

The relatively abrupt change to negative glacier mass balances strongly suggests a climate tipping point, when the climate changes from one stable state to another.

There are other compelling signs that a climate tipping point has been reached. One of the most critical is the loss of the floating sea ice cover in the Arctic Ocean. In 2014, the late-summer extent of sea ice in the north polar seas was the lowest since satellite measurements began in 1979.

Before 1979, evidence based on shipping and whaling charts suggests it has not been this low for at least hundreds of years. Paleo climatologists believe that Arctic sea ice cover last melted completely during summers about 125,000 years ago, during a warm period between ice ages.

Reduction of northern-hemisphere sea ice means that more incoming sunlight is absorbed into darker ocean water instead of being reflected by ice and then re-radiated into the atmosphere as heat. This, in turn, reduces the extent of the annual northern-hemisphere snow cover, which further accelerates global warming.

A related effect that could be even more environmentally devastating is the release of methane from permafrost and seafloor hydrates as the ocean warms. Another tipping-point indicator is the Greenland and West Antarctic ice sheets, which have shown signs of disintegrating during the past two decades. Just partial melting of these ice sheets will raise sea level several meters.

If the warning glaciers gave us in the 1980s had been heeded and a crash program to replace fossil fuels with renewable energy had been initiated then, the climate-change crises we are facing now would be less acute.

Transitions to alternative energy such as solar and wind are underway now, but they were late getting started and are not yet substantial enough to reduce the rate of greenhouse gas emissions worldwide.

The current concentration of carbon dioxide in the atmosphere is approximately 400 parts per million, the highest it has been for at least 800,000 years and likely more than 20 million years.

It is increasing at about two parts per million annually, and it is accelerating. It should be declining if we want to avert a humanitarian crisis caused by food shortages in an out-of-control climate.

The implications are stark. For civilization to survive, fossil fuel burning must taper off dramatically and be replaced with renewable sources of energy. The United Nation’s Intergovernmental Panel of Climate Change (IPCC) could provide guidance on how this might be accomplished.

The panel, which holds expert meetings regularly to study climate issues and make recommendations, is composed of climatologists and other scientists from more than 100 member countries. Thousands of scientists from all over the world contribute to the work of the IPCC on a voluntary basis.

The recent visit of President Barack Obama, Secretary of State John Kerry and Secretary of the Interior Sally Jewell to Alaska to observe glaciers and the effect of climate change symbolically emphasized the problem of global warming and its impact on the well-being of humans.

The conference they attended was organized to increase awareness of the environmental problems that face Alaskans, such as coastal erosion, wildfires, sea level rise and permafrost thawing. These are problems that the much of the world will soon be facing.

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