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Bridging climate science, citizens, and policy

New Arctic Ice Assessment: Faster Melt = Faster Sea Level Rise

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Most of the projections in the science portion of the IPCC’s 2007 4th Assessment Report have been shown many times since its issuance to be too conservative.  Temperatures have risen faster; ice (sea- and land-based) has melted faster; ocean acidification and warming has happened faster, the number of extreme weather events has increased faster, etc.

I’ve written before about most of these.  I will take this space to write once again about polar ice melting faster than projected (according to observations) and the impact that will have on global coastlines.

According to the executive summary of a new assessment of Arctic climate, the international Arctic Monitoring and Assessment Program (AMAP) reports that Arctic temperatures in the past six years were higher than at any time since measurements began in 1880.  Moreover, feedback mechanisms have already started.

What this means is the arctic sea ice area and global sea level projections made by the IPCC just 4 years ago underestimate this year’s conditions, which means they also very likely underestimate future conditions too.  In an updated projection that has deep significance for billions of people worldwide:

The melting of Arctic glaciers and ice caps, including Greenland’s massive ice sheet, are projected to help raise global sea levels by 35 to 63 inches (90-160 centimeters) by 2100, AMAP said, though it noted that the estimate was highly uncertain.

That’s up from a 2007 projection of 7 to 23 inches (19-59 centimeters) by the U.N. panel, which didn’t consider the dynamics of ice caps in the Arctic and Antarctica.

Is the difference between one-half to 2 feet and 3 feet to 5 feet significant?  Only those of us who are sane seem to think so.  This is but one effect of oil corporations continuing to post record profits quarter after quarter, year after year.  How much infrastructure exists near 5ft above sea level worldwide?  How much is that infrastructure worth?  How much cropland exists at those low altitudes?  How many miles of ruined cropland from rising seas only will occur before widespread food shortages occur?  How much is our lifestyles worth; how much do they really cost?

AMAP scientists will discuss their findings in Copenhagen, Denmark starting tomorrow.

My most recent `State of the Poles` post discussed shorter-term influences on sea ice conditions (monthly to seasonal effects).  I’ve stated in that series that a new regime now exists for the Arctic.  Findings like these support that assessment.

For the hard-core curious, the key findings of the report are reprinted below the fold (h/t ClimateProgress)

Here are the “key findings” of this must-read warning to humanity:

  1. The past six years (2005–2010 have been the warmest period ever recorded in the Arctic Higher surface air temperature are driving changes in the cryosphere.
  2. There is evidence that two components of the Arctic cryosphere – snow and sea ice  are interacting with the climate system to accelerate warming.
  3. The extent and duration of snow cover and sea ice have decreased across the Arctic. Temperatures in the permafrost have risen by up to 2 °C. The southern limit of permafrost has moved northward in Russia and Canada.
  4. The largest and most permanent bodies of ice in the Arctic – multiyear sea ice, mountain glaciers, ice caps and the Greenland Ice Sheet – have all been declining faster since 2000 than they did in the previous decade.
  5. Model projections reported by the Intergovernmental Panel on Climate Change (IPCC) in 2007 underestimated the rates of change now observed in sea ice.
  6. Maximum snow depth is expected to increase over many areas by 2050, with greatest increases over Siberia. Despite this, average snow cover duration is projected to decline by up to 20% by 2050.
  7. The Arctic Ocean is projected to become nearly ice-free in summer within this century, likely within the next thirty to forty years.
  8. Changes in the cryosphere cause fundamental changes to the characteristics of Arctic ecosystems and in some cases loss of entire habitats. This has consequences for people who receive benefits from Arctic ecosystems.
  9. The observed and expected future changes to the Arctic cryosphere impact Arctic society on many levels. There are challenges, particularly for local communities and traditional ways of life. There are also new opportunities.
  10. Transport options and access to resources are radically changed by differences in the distribution and seasonal occurrence of snow, water, ice and permafrost in the Arctic. This affects both daily living and commercial activities.
  11. Arctic infrastructure faces increased risks of damage due to changes in the cryosphere, particularly the loss of permafrost and land-fast sea ice.
  12. Loss of ice and snow in the Arctic enhances climate warming by increasing absorption of the sun’s energy at the surface of the planet. It could also dramatically increase emissions of carbon dioxide and methane and change large-scale ocean currents. The combined outcome of these effects is not yet known.
  13. Arctic glaciers, ice caps and the Greenland Ice Sheet contributed over 40% of the global sea level rise of around 3 mm per year observed between 2003 and 2008. In the future, global sea level is projected to rise by 0.9–1.6 m by 2100 and Arctic
    ice loss will make a substantial contribution to this.
  14. Everyone who lives, works or does business in the Arctic will need to adapt to changes in the cryosphere. Adaptation also requires leadership from governments and international bodies, and increased investment in infrastructure.
  15. There remains a great deal of uncertainty about how fast the Arctic cryosphere will change in the future and what the ultimate impacts of the changes will be. Interactions (‘feedbacks’) between elements of the cryosphere and climate system are particularly uncertain. Concerted monitoring and research is needed to reduce this uncertainty.
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