NASA’s James Hansen: sea level rise will be faster than we think

Today, famous NASA climate scientist James Hansen (one of the first to call attention to the dangers of climate change back in the 1980s) and a team of other climate experts from around the globe released a report that makes dire predictions for the state of the Earth over the next century.

Hansen’s team predicts that glacial ice in the Arctic will be melting at speeds ten times greater than previously estimated, due to a feedback loop effect. It works like this:

  1. 40n4_Feedback_Loops_INFOGRAPHIC_lg

    click to enlarge. Graphic courtesy of Alternatives Journal.

    The climate warms, melting land ice in the Arctic, which then flows into the ocean.

  2. Ice reflectivity, or “albedo”, is a great cooling factor for the planet (like wearing a white T-shirt on a hot day). So, when large amounts of ice melt and reveal the darker-colored ground beneath, the planet’s surface absorbs more light from the sun, where it once reflected it. Other mechanisms of this feedback loop are detailed in the graphic to the right.
  3. This increased light absorption results in more heat being trapped in the atmosphere, which in turn melts more ice.

If Hansen’s team’s predictions are correct, many of us alive today will bear witness to the costs of climate change on civilization, contrary to most models which speak in terms of “what will happen in 2100” . This is precisely why Hansen is calling for “emergency cooperation among nations” to solve this problem now, before it becomes dire. Hansen writes:

“We conclude that continued high emissions will make multi-meter sea level rise practically unavoidable and likely to occur this century. Social disruption and economic consequences of such large sea level rise could be devastating. It is not difficult to imagine that conflicts arising from forced migrations and economic collapse might make the planet ungovernable, threatening the fabric of civilization.”

On top of the dangers of sea level rise, the study also predicts a threat to the planet’s interchange of warm, salty water and cold, less-salty water, known as the planet’s thermohaline circulation, or the “global conveyor belt. This global interchange is responsible not only for the currents in the oceans and all of the benefits they provide to sea life, but also for the milder climate in Western Europe than you find at similar latitudes in Eastern Europe and Asia. This video from the educational organization Kurzgesagt (German for “In a nutshell) explains the phenomenon quite well (the video itself is in English):

As the video outlines, constant inflows of cold freshwater at the poles could slow this vital thermohaline circulation, or stop it altogether. This would mean trouble for Western Europe’s mild winters, making them more like their counterparts in Northern Russia and the Scandinavian countries. The last time that the global conveyor belt was halted, it may have caused a “little ice age” in Western Europe.
One caveat to the findings: the report by Hansen et al. was published in the “discussion-based” Atmospheric Chemistry and Physics journal, and as such has not been thoroughly peer-reviewed. However, the Washington Post has contacted many leading climate scientists and has aggregated their responses here.