While the actual temperature remains in neutral thanks to La Niña, the evidence for significant changes in the atmosphere mounts.
International cooperation to combat global warming crawls along, as the movement of weather systems appears to be slowing.
This month’s Climate Change Checkup reveals some ominous signs. Let’s look.
Modest Global Temperatures Accompany La Niña
The trend for 2017 to be the third warmest in 137 years of accurate record-keeping is intact through November.
This November was the fourth warmest since 1880. The year-to-date is third warmest, and 2017 will almost certainly finish the full year in third place behind 2016 and 2015.
New warm temperature records for the month were set on four continents and in all major oceans. There were no cold temperature records.
The temporary stalling of the monthly trend towards a hotter planet can be traced to a modest La Niña in the tropical Pacific Ocean.
All forecasts suggest the La Niña will wane in the spring, and conditions will be either neutral or slightly El Niño by summer. Climatologists will be watching the reaction of the global temperatures to this change in the ocean. The long-term increase in temperature of about one degree Celsius per century is still in place, but a return to the upward trajectory of temperatures of the last few years, approximately three times the long-term trend, would be an indication that international efforts to curb the emissions of greenhouse gases are not yet working.
France Takes Lead On Climate Change
At 39, President Emmanuel Macron of France is the youngest leader of a western democracy. France plans to fill the void in climate leadership left by the US withdrawal (actually an announcement of intention to withdraw; the action won’t become final for two years) from the 2015 Paris agreement. Convening a largely symbolic meeting of government representatives and private philanthropies, Macron was careful to leave the door open for the US to play a renewed role on climate issues. According to France24, Macron said, “I’m pretty sure that my friend President Trump will change his mind in the coming months or years, I do hope.”
As efforts to stop the world from warming by curtailing the emissions of greenhouse gases, primarily carbon dioxide (CO2), stumble forward, a major issue is how to convince developing nations to forgo a transitional fossil fuel stage of energy production (which is cheap) and go directly to much-less-polluting renewables (which are expensive).
The Paris Agreement of 2015 outlined methods for developed nations to help bridge the financial gap, and much of the recent meeting was focused on how to fund a world of only renewable energy sources. Though the conferees made some progress, it is safe to say that answering the question of who pays for what in reducing global CO2 emissions won’t be easy.
Evidence That The Weather Is Becoming More Persistent Mounts With The Snow
A reader in Buffalo asked me if her observation that Lake Effect snow events are getting more long-lasting is correct. Indeed, the anecdotal data seem to indicate that, but with a caveat.
Lake Effect snow is very dependent on wind direction and terrain, as the accompanying graphic of snowfall near Buffalo during the winter of 2015-16 shows, with seasonal totals varying from under 40 inches to over 140 inches.
When the weather pattern gets stuck in a flow of cold air over the Lakes, which it seems to do with more regularity these days, somebody is going to get a lot of snow.
But my reader should be happy she doesn’t live on the western slopes of the Japanese mountains, where a massive ‘Lake Effect’ from the Sea of Japan can leave over 100 FEET of snow in a single winter.
The anecdotal evidence that weather patterns are changing more slowly is adding up: Hurricane Harvey stalled over Texas; Hurricane Jose stalled southeast of New England; the horrible drought in California has lasted for years, and the recent fires were exacerbated by persistent east winds.
The recent snow in the deep south and stretching in a ribbon to the northeast megalopolis is another example of air masses not moving. Cold and warm air masses met along a front that refused to move. As the cold air wedged under the warm air, and the warm air overran the cold, snow fell along the entire stretch of the front for many hours.
Recent statistical studies indicate that an event like Harvey is now three times as likely to occur than it was a century ago. But proof that this is so will await a physical explanation. Still, global warming is not in doubt, and the evidence that it is having widespread effects is getting stronger.
What Makes Weather Systems Stall?
The jet stream is a west-to-east flow in the middle levels of the atmosphere. At the surface, cold air lies to the north, and warm air to the south (in the northern hemisphere).
Wiggles in the jet stream show where cold and warm air push south and north respectively at the surface. The more pronounced the wiggle, the slower the system tends to move eastward. In an extreme case, a low or high pressure system ‘cuts off’ from the rest of the jet stream and is stuck in place.
A pattern in which the the jet stream bows far to the north resembles the Greek letter omega (Ω), and this configuration is sensibly known as an Ω-block, because weather systems cannot get past it.
Downstream from the Ω-block the jet stream bows to the south, normally bringing cold air with it at the surface. This winter’s jet stream has featured an Ω-block over the western US. High pressure has dominated in the west, creating the conditions for high fire danger in California. Meanwhile, cold air has pushed south in the middle and eastern parts of the country.
In recent years, there have been more occurrences of blocking pattens in the jet stream, but there is no explanation of why this should be the atmosphere’s response to global warming.
Looking Ahead: The Stage Is Set For Rapid Warming
The urge to write an alarmist headline overtook me for a moment. In fact, a rapid temperature rise is imminent. But not to worry; it’s just the seasonal change in the northern hemisphere.
The winter solstice on December 21 reminds us that the days will soon get longer in New York, London, and Moscow. There is a lag between the time of minimum solar heating and the days of lowest temperature, so most places won’t feel any warming until February. And, of course, our friends in Buenos Aires, Capetown, and Canberra will see temperatures fall.
The next Climate Change Checkup will be published after NOAA’s release of the full-year 2017 analysis in mid-January, 2018.