February 2017 was not as warm as February 2016 — but it was warmer than any other February on record by a significant margin.
The warmth was spread evenly over the nine categories calculated by NOAA — with one outlier.
On the whole, the decades-long increase in temperature that is leading to uncharted waters (and air) is still intact.
Warmth Spread Evenly By Hemisphere, Land, And Sea
February 2017 was second-warmest only to the El Niño-inflamed blockbuster of February 2016 in seven of nine categories: global land; global sea; global land and sea; northern hemisphere sea; northern hemisphere land and sea; southern hemisphere sea, southern hemisphere land and sea. Northern hemisphere land was third. The outlier was southern hemisphere land at eighth warmest.
Though the southern hemisphere land temperature is a data point that should be regarded with a partially-raised eyebrow, it does not indicate a trend. For the three-month summer period of December 2016 through February 2017 (summer in the southern hemisphere), February was second warmest, as it was elsewhere.
Furthermore, land accounts for only 20% of the surface area of the southern hemisphere, and a good part of that is the sparsely-sampled continent of Antarctica.
Effect Of El Niño And La Niña
Most, but not all, powerful El Niños are followed by strong La Niñas. The recent La Niña built weakly and faded quickly. By NOAA’s definition, it barely qualified as La Niña.
Conditions in the Pacific Ocean are back to neutral, with modestly warm water in the east and minor deviations from normal elsewhere. Most numerical models have consistently moved towards predicting another El Niño by late northern hemisphere summer or fall.
US Record Warm In Much Of South And East
The United States was particularly warm in February — second warmest nationwide on record. A wide swath from southern Texas through the midwest and to the mid-Atlantic experienced the warmest February ever. Nationwide, the cooler than normal temperatures in the northwest kept February 2017 from being warmer than February of 1954, which averaged two-tenths of a degree (F) warmer.
Arctic And Antarctic Sea Ice
The Danish Meteorological Institute has recorded the temperature of the Arctic since 1958.
The rate of warming is now more than double that of the rest of the globe and sea ice extent is shrinking.
Recently, the temperature has not been below the long-term average for more than five months, and has risen as high as 20 C (36 F) above the average.
This is not surprising to meteorologists who regularly take albedo (the reflective properties of the earth’s surface) into account.
Ice has a high albedo — it reflects much of the radiation that strikes it. Water has a low albedo, absorbing most of the radiation. One feedback effect of global warming is that as the arctic ice melts, the albedo of the ice-ocean decreases, amplifying the warming. Less radiation is reflected and more is absorbed.
Most meteorologists agree that the Arctic will be ice-free at least part of the year within a few decades.
Though the Arctic and Antarctic are as different as land and sea, they have had the similarity of high albedo as long as the Arctic had significant ice.
Both Arctic and Antarctic sea ice were at record lows for February, but the Antarctic land mass will retain its snow-covered high albedo. The imbalance of one pole with high albedo and the other with low albedo raises questions about how this might affect the circulations of the atmosphere and ocean.
An additional potential feedback of the melting Arctic sea ice is the possibility of the release of methane, large amounts of which are now sequestered in the seabed. Methane is many times more effective as a greenhouse gas than carbon dioxide.
December Through February Precipitation
Single month precipitation totals vary substantially from month to month. Three-month totals give a better picture of trends. Percentiles, which measure the percentage deviations from average, give a clearer picture than simple precipitation totals.
The percentile precipitation map for December through February shows some eyebrow-raising departures from normal. India had the most noteworthy drought, with a record-dry period in much of the southern half of the country. A much dryer than normal season was also reported in the eastern US, most of Europe, the Middle East, central Asia, and eastern South America
Northern North America, western Australia, extreme northern Europe, and southern portions of South America and Africa were notably wet.
The widespread dry conditions come as a mild surprise to climatologists, since a warmer atmosphere can hold more water vapor. An increase in atmospheric water vapor would make increased precipitation possible, even likely. Since precipitation is important to agriculture, any substantial deviations from normal need to be carefully watched.
What’s Next For The Warming Planet
Some of the early results of global warming have already been felt. Sea level rise regularly floods parts of coastal cities such as Miami Beach and threatens to submerge some Pacific Islands. Progress has been made in reducing CO2 emissions in the aftermath of the Paris Climate Accord, but whether it is enough to stave off more serious effects of climate change is still an open question.