NewScientist (2 April 2016) reports on the work of climate change scientist James Hansen in an alarming manner:
A MASSIVE rise in sea level is coming, and it will trigger climate chaos around the world. That was the message from a controversial recent paper by climate scientist James Hansen. It was slated by many for assuming – rather than showing – that sea level could rise by between 1 and 5 metres by 2100.
But now, just a week after being formally published, it is being backed up by another study. “He was speculating on massive fresh water discharge to the ocean that I don’t think anybody thought was possible before,” says Rob DeConto of the University of Massachusetts-Amherst. “Now we’re about to publish a paper that says these rates of fresh water input are possible.”
The new study is here.
Here we use a model coupling ice sheet and climate dynamics—including previously underappreciated processes linking atmospheric warming with hydrofracturing of buttressing ice shelves and structural collapse of marine-terminating ice cliffs—that is calibrated against Pliocene and Last Interglacial sea-level estimates and applied to future greenhouse gas emission scenarios. Antarctica has the potential to contribute more than a metre of sea-level rise by 2100 and more than 15 metres by 2500, if emissions continue unabated. In this case atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delay its recovery for thousands of years.
Add in the water coming off the ice cap of Greenland and it’s all more than a little disturbing. Here‘s glaciologist Jason Box of Denmark:
“Increased glacial surface melt water infiltration induces ice internal warming. Warmer ice deforms more easily, promoting a dynamical flow response to climate warming and increasing irreversible feedbacks from surface elevation drawdown into warmer parts of the atmosphere. The increase in melt area and volume with warming is non-linear because ice cap or ice sheet elevation profiles are flatter as elevation increases. In a warming scenario, a melt-elevation feedback threatens to produce irreversible ice cap and ice sheet loss. Irreversibility depends on sufficient ice surface elevation drawdown and warming sustained above some stable threshold. The larger the land ice body, the longer time needed for the irreversibility threshold to be crossed.
“The Greenland ice sheet is essentially lost in a climate as warm or warmer than that during 2000-2015. Yet, the loss rate depends strongly on amount of warming above a stable level. In the case of Greenland, summer warming above pre-industrial is 1.2-1.6 C. If warming were stabilized at 1 C above the preindustrial era, the loss of a significant fraction of the Greenland ice sheet appears to require 10s of thousands of years. Larger and expected warming (3-6 C above preindustrial summer temperatures by year 2100) reduces the time of significant ice sheet loss from millennia to centuries.”
In the meantime, the University of Maine’s Climate Change Institute is developing this interesting tool for climate modeling:
Climate Reanalyzer is being developed by the Climate Change Institute at the University of Maine to provide an intuitive platform for visualizing a variety of weather and climate datasets and models.
Investigate climate using interfaces for reanalysis and historical station data. Plot maps, timeseries, and correlations; export timeseries data to a text file for later use in spreadsheet software; export map layers to Google Earth.
Checking the latest weather forecast is really easy. Just enter a placename beside the “Search Weather” button at the top-right of every page. You can also view and animate forecast maps for different parts of the world.
Here’s a sample picture showing today’s temperature anomalies. I must find some time to experiment with this more.
