Greenland ice sheet sets new record with early melt

Thursday, April 14, 2016, 5:30 PM - Greenland's earliest recorded melt shocked scientists this week, while at the same time, a new report ultimately confirms the 97 per cent consensus that human activity is responsible for recent changes in our climate due to global warming.

Greenland's earliest major melt on record

As this week started, scientists monitoring the Greenland ice sheet experienced a shock - over 10 per cent of the island's ice sheet surface was experiencing melting of over 1 millimetre. As this started on April 11, this surpasses the previous record for early melt of more than 10 per cent of the ice sheet surface - from May 5, 2010 - by more than three weeks.

Left: Maps showing melting on April 10 and 11, 2016. Right: Graph of percentage of total ice sheet area experiencing at least 1 mm of melting - Jan 1 to Apr 11 (blue line), 1990-2013 average (grey line) and year-to-year daily variation (grey shaded area). Credit: Danish Meteorological Institute

This situation was so unusual, so anomalous, that the scientists doubted what they were seeing, at first.

"We had to check that our models were still working properly," Peter Langen, a climate scientist at the Danish Meteorological Institute (DMI), told Polar Portal. "Fortunately we could see from the PROMICE.dk stations on the ice sheet that it had been well above melting, even above 10^oC. This helped to explain the results."

What's the cause of this? An unusual warm spell over Greenland during the past week, along with warm onshore winds bringing rain to the southwest coast of the island.

Temperature anomalies (from 1979-2000 average) for April 8-14, 2016 show a patch of unusually warm air over Greenland. Credit: Climate Reanalyzer

DMI forecasters say that temperatures will cool throughout the rest of the week, but this event has already taken its toll.

Not only is this the earliest substantial melt on record, but the refreezing of the rain and meltwater soaking into the ice sheet sets it up for even more melting in the future.

Prof. Jason Box, of the Geological Survey of Denmark and Greenland (GEUS), explained to Polar Portal: "Meltwater refreezing releases heat into the snow at depth, reducing the amount of heating needed for melt to start and forming ice layers that can help melt water run off the ice sheet earlier with climate warming."

Needless to say, DMI and GEUS scientists will be closely monitoring the ice sheet going forward.

Ice melt for April 12-13, 2016. Credit: Danish Meteorological Institute

Consensus on the 97 per cent consensus

"97 per cent of climate experts agree humans are causing global warming." - SkepticalScience.com

This statement, which came about as a result of the Consensus Project in 2013, has come under persistent attack from those who deny the link between fossil fuel burning and the current state of global warming and climate change we are observing around the world.

In response to these attacks, John Cook, from the Global Change Institute at the University of Queensland and the founder of SkepticalScience.com, gathered a team of over a dozen colleagues, all of whom had been part of other consensus studies, to go over the data and put the arguments to the test.

The result? A consensus on the consensus.

John Cook explains in the video below:

"We have shown that the scientific consensus on AGW is robust, with a range of 90%–100% depending on the exact question, timing and sampling methodology," Cook and his colleagues wrote in the new study. "This is supported by multiple independent studies despite variations in the study timing, definition of consensus, or differences in methodology including surveys of scientists, analyses of literature or of citation networks."

"From a broader perspective, it doesn't matter if the consensus number is 90% or 100%," they concluded. "The level of scientific agreement on AGW is overwhelmingly high because the supporting evidence is overwhelmingly strong."

Global CO₂ concentration

Credit: Scripps Institution of Oceanography, UC San Diego

Sources: Polar Portal | DMI | IOPScience | Global Change Institute