Greenland’s Ice Melt Contribution To
Sea Level Just 1.5 cm For 1900-2010
As the HadCRUT4 temperature data indicate, there has been no net warming trend in the Arctic for the last 80 years. In fact, from the early 1940s to the mid-1990s, the Arctic cooled.
Due to its Arctic location, Greenland temperatures have likewise followed a similar trend as the rest of the region — warming during the 1920s to 1940s, cooling from the 1940s to 1990s, and then warming (commensurate with the 1930s) since the 1990s.
Climate Alarm Advocates: Arctic Will Contribute 19-25 cm To Sea Levels By 2100
Despite the relatively unremarkable temperature trends in the Arctic in general or Greenland in particular in the last 100 years, the narrative that says man-made CO2 emissions are causing catastrophic Arctic ice melt and consequent sea level rise has gained widespread popularity in media circles.
For example, in yet another alarmist headline from this last week it was claimed that some Arctic glaciers will “disappear completely” in the next 83 years and this “extreme” Arctic ice melt will lead to 19 to 25 centimeters of sea level rise by 2100.
“By the end of this century, as some glaciers disappear completely, the Arctic’s contribution to global sea level rise will reach at least 19 to 25 centimeters, according to the report by the Arctic Council’s Arctic Monitoring Assessment Program (AMAP).”
New Paper Concludes Greenland Contributed Just 1.5 cm To Sea Levels Since 1900
A new scientific paper published in The Cryosphere last week indicates that the Greenland Ice Sheet (GIS) gained mass during much of the 1940s to 2000s period — especially 1961-1990, the common reference period when it was previously assumed the GIS was stable.
In fact, the scientists conclude that the overall GIS melt for the entire 1900-2010 period contributed a negligible 1.5 centimeters (about half an inch) to sea levels during that entire 110-year period.
“Results from all MAR simulations indicate that the period 1961–1990, commonly chosen as a stable reference period for Greenland SMB [surface mass balance] and ice dynamics, is actually a period of anomalously positive SMB (∼ +40 Gt yr−1 ) compared to 1900–2010. … [T]he ERA-20C forced simulation suggests that SMB [surface mass balance] during the 1920–1930 warm period over Greenland was comparable to the SMB of the 2000s, due to both higher melt and lower precipitation than normal.”
“The period 1961–1990 has been considered as a period when the total mass balance of the Greenland ice sheet was stable (Rignot and Kanagaratnam, 2006) and near zero. However, at the last century scale, all MAR reconstructions suggest that SMB [surface mass balance] was particularly positive during this period [1961-1990] (SMB was most positive from the 1970s to the middle of the 1990s), suggesting that mass gain may well have occurred during this period, in agreement with results from Colgan et al. (2015).”
“Finally, with respect to the 1961–1990 period, the integrated contribution of the GrIS SMB anomalies over 1900–2010 is a sea level rise of about 15 ± 5 mm [1.5 cm], with a null contribution from the 1940s to the 2000s, suggesting that the recent contribution of GrIS to sea level change (van den Broeke et al., 2016) is unprecedented in the last century.”
Between 1920-1930, Greenland Warmed By 2 to 4°C In Less Than 10 Years
“A significant and rapid temperature increase was observed at all Greenland stations between 1920 and 1930. The average annual temperature rose between 2 and 4 °C in less than ten years. Since the change in anthropogenic production of greenhouses gases at that time was considerably lower than today, this rapid temperature increase suggests a large natural variability of the regional climate.”
Glacier Melt Rapid, Contribution To Sea Level Rise Substantially Higher Before 1950
“The abrupt climatic transition of the early 20th century and the 25-year warm period 1925–1950 triggered the main retreat and volume loss of these glaciers since the end of the ‘Little Ice Age’. Meanwhile, cooling during the 1960s, 1970s and 1980s altered the trend, with advances of the glacier snouts.”
“During the period 1898–1946, the snout of Gljúfurárjökull retreated 635 m, almost two-thirds of the total distance from the LIA maximum (1898–1903) to 2005, at an average rate of 13.2 m yr−1. … The trend in Western Tungnahryggsjökull during the first half of the 20th century was a more rapid retreat, showing the highest average rates of the whole period (19.5 m yr−1). By 1946, this glacier had retreated almost 90% of the total recorded between the LIA maximum (1868) and 2005. … Just as in the glaciers described above, the retreat of the Eastern Tungnahryggsjökull from its LIA position was more intense during the first half of the 20th century, and in 1946 its snout was only 200 m from its current position.”
Conclusion: Abrupt Arctic Warming, Cooling, Ice Melt Uncorrelated With CO2 Emissions
Implicit in the alarmist projection that rapid Arctic warming and ice melt will raise sea levels by 19 to 25 centimeters during the next 8 decades is the assumption that the Arctic’s post-1990s warming trend and ice melt has been driven by anthropogenic CO2 emissions — which are expected to continue to rise without dramatic energy policy changes. However, this assumption ignores the nearly 100 years (1900 to mid-1990s) of non-correlation between CO2 emissions and the Arctic climate.
Succinctly, during the 1920s to 1940s period the (a) Arctic warmed rapidly (~3°C per decade), the (b) Greenland ice sheet melted rapidly, and the (c) glacier melt contribution to sea level rise was explosive. This occurred while anthropogenic CO2 emissions were both flat and negligible (10 times smaller than today’s emissions).
Then, just as CO2 emissions began to rise at an accelerated pace after 1940, the (a) Arctic cooled (for nearly 60 years), the (b) Greenland ice sheet surface mass balance was positive with a “null” contribution to sea level rise (1940-2000), and (c) the Arctic-wide ice melt contribution to sea level rise abruptly decelerated.
For the 110 years between 1900 and 2010, the Greenland ice sheet contributed just 0.6 of an inch (1.5 cm) to sea levels despite a 10-fold increase in anthropogenic CO2 emissions during that period. Therefore, the very mechanism (human CO2 emissions) assumed to be driving a projected 19 to 25 centimeters of Arctic ice melt contribution has not been observed to be a driving mechanism previously.
The observational evidence indicates that variations in anthropogenic CO2 emissions do not drive Arctic warming (or cooling), ice sheet surface mass balance, or sea level rise from retreating glaciers.