What is natural
by Jim Steele
Glaciers around the world reached their largest size in four thousand years in 1850. Then suddenly the world began to warm up. The Arctic sea ice had lost 40% of its thickness by 1940. Around the arctic island of Svalbard, the melting sea ice extended the shipping season from 3 months to 7 by 1940, while an additional 400 square miles of sea ice melted along Russian coasts. By 1950, 96% of Europe's glaciers had retreated and small glaciers had simply disappeared. In the tropics, the famous glaciers of Kilimanjaro in Africa also shrank alarmingly.
In the far north, pine forests could not multiply between 1850 and 1900 due to the cold. However, with warming, all ages of the seedlings multiplied. The tree line rose about 70 feet in just a few decades. Plants bloomed earlier, and seeds and berries ripened earlier. The cod moved north and created a new Greenland fishery. Several southern bird species have migrated to Iceland.
This warmth was an extraordinary climate reversal and scientists tried to understand this change. In the 1950s, H.W. a leading glacier expert. Ahlmann explained the growing consensus that the dramatic warming is due to "increased heat transfer through the atmosphere due to intensification of the winds that transport heat from the southern parts to the Arctic". Today's best climatologists are observing similar natural climate change, pushing warm winds and warm ocean currents north and melting the Arctic again.
To be fair, British engineer G.S. Callendar in the 1940s also suggested that global warming of CO2 was melting the glaciers. But he was a lonely voice and peer reviewers had refused to publish his paper attributing global warming to CO2 for the melting glaciers of Kilimanjaro.
Today there is growing scientific support for theories that changing winds in the Arctic cause decades of warming or cooling. The NAO index (North Atlantic Oscillation) is a measure of naturally changing winds. The NAO alternates between a positive phase in which the west wind increases and warmer winters bring to Western Europe. When changing into the negative phase, the westerly winds decrease, whereby Western Europe cools down. During this phase, however, warmer winds blow from south to north more frequently. Scientists admit that up to 100% of observed climate change could be due to this natural variability.
As political struggles over control of energy policies increased, interest in fossil fuels and the theory of global warming from CO2 was revived. Scientists promoting global CO2 warming have exhumed Callendar's private article and elevated his status to a founding hero of global warming theory. Some scientists believed that increasing CO2 could affect the winds and phase of the NAO. Since the positive NAO had generated strong westerly winds that warmed much of Europe and Asia, they predicted that the currently positive NAO would continue and further exacerbate global warming.
However, this hypothesis quickly failed. The NAO returned to its negative phase at the beginning of the 21st century. This made the westerly winds weaker. This resulted in more consistent high pressure blocking systems and a Wavier jet stream as shown in the diagram. Blocking weather systems move more slowly than normal storms, forcing the prevailing winds and other storms to move around them. This was outlined again in the 1950s by climate researchers who pioneered our current understanding of blocking systems. Weather satellites now confirm these weather effects. They also showed that surface temperatures rose 10 to 12 ° C above normal when blockage systems of the early 20th century forced warm air from the south over Greenland.
On the graph, orange colors are warmer and blue colors are cooler. Blockage systems in the Pacific push warmer air (orange) into Alaska and draw cold air into the southern United States. As a result, temperatures in Alaska are sometimes higher than in northern Florida. Likewise, the blockage in the Atlantic pushed warm air over Greenland, causing extreme melting but bringing a cold snapshot to Europe. The Americans became aware of the power of a negative NAO and stalled when a weak hurricane was prevented from normally migrating at sea. Instead, it was diverted to New Jersey and turned into the devastating superstorm Sandy. In 2019, a warm mass of air moved north from the baking Sahara. The air in the Sahara crossed Europe and brought record temperatures. Further north, this warm air caused the seventh largest melting period in Greenland since 1978.
The theory that the NAO and changing winds create the conditions that drive the warming and cooling of Greenland is supported by all observable evidence. Greenland lost ice in the 1930s and gained ice in the 1970s and 80s. Although Greenland's ice has melted heavily in the last few decades, that melting rate is now slowing and the changing NAO suggests the ice will recover. In contrast, the competing theory of global warming of CO2 suggests that as CO2 continues to rise, Greenland's ice will increasingly melt and sea level rise dramatically. This theory has led to calls to leave our shores and invest in managed retreats. But before you panic, know your climate history and listen to the science. All the science!
Published in the newspapers of Battle Born Media on October 13th, 2020
Jim Steele is a retired director of the Sierra Nevada Field Campus, SFSU
and authored landscapes and cycles: An environmentalist's journey to climate skepticism
Contact: [email protected]