Climate Change Checkup, June 2017


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According to NASA, May 2017 was the second warmest May since 1880. Graphic courtesy of NASA.

Tip O’Neill famously said all politics is local, and the same might be said for the weather. All a Bostonian wants from the weather is a sunny day at Fenway with the Red Sox beating the Yankees.

But just as life in O’Neill’s home district in Massachusetts was affected by decisions made in Washington (or even in Beijing), so the weather in Boston is affected by what goes on in the atmosphere in far-off locations — including many miles above the ground. And, increasingly crucially, what is pumped into the atmosphere around the globe.

The big news earlier this month was the US withdrawal from the Paris climate agreement.

Some scientists have expressed the opinion that it won’t really make that much difference: Emissions reductions are voluntary; enforcement is non-existent; withdrawal is easy.

On the other hand, the agreement provides a framework, to which 194 of 197 nations belonging to the United Nations Framework Convention on Climate Change (UNFCCC) have signed on, for addressing the inevitably most important question: Who pays for the necessary conversion from widespread dependence on fossil fuels to a renewable-energy world?

Before we get to these big questions, let’s review the temperature data for May, 2017.

May 2017 Continues The Temperature Trend

Though Africa recorded its warmest May ever, colder than normal temperatures in much of northern Russia helped put May in third place globally. Graphic courtesy of NOAA.

According to NOAA, May 2017 was the third warmest May in 138 years of records. NASA, using slightly different sampling techniques, found that May 2017 was second warmest. The NOAA data were significantly affected by the temperature of the northern hemisphere land, which came in 8th warmest.

In general, the temperature shows a leveling off after the blockbuster warm El Niño years of 2015 and 2016, but the longer term trend is inexorably upwards.

Where’s The Heat?

By some calculations, the earth’s atmosphere is not warming as much as some scientists anticipated. The problem of the missing heat is fathomable, if you’ll excuse the pun — it may be hiding in the deep ocean.

While land surface is widely sampled at thousands of reporting stations, upper atmosphere is fairly well sampled by radiosonde (weather balloon), and ocean surface is modestly sampled by ships and buoys, there is virtually no data on temperatures in the deep ocean. Incoming solar radiation is mostly dispersed in a complicated way.

The ocean could become a permanent heat sink which would mitigate the effect of global warming on land. On the other hand, as the ocean warms, it expands, one of the two reasons sea level is rising (the other is from melting glaciers and sea ice). The most likely effect of heat stored in the ocean is that it will eventually appear at the surface. Surface water temperatures have vast implications for the weather. So Decoded Science will report monthly on sea surface temperatures, looking carefully for significant changes or departures from long-term averages.

Sea surface temperatures are currently above normal at low latitudes and below average at higher latitudes in both hemispheres. Graphic courtesy of NOAA.


NOAA’s most recent sea surface temperature analysis, released June 19, has a single striking feature: red (warmer than average temperatures) dominates the tropical and subtropical seas; blue (colder than normal temperatures) dominates higher latitude waters. This divergence of temperature anomalies by latitude has persisted for many months, and Decoded Science has suggested the temperature anomaly at high latitudes could be the result of cold water runoff from melting snow, ice, and glaciers in Antarctica, Greenland, and the Arctic Ocean.

Of more immediate interest is the distribution of temperatures in the tropical and subtropical waters of the northern hemisphere as tropical cyclone season approaches its peak. The Atlantic Ocean is warmer than normal all the way from Africa to the Caribbean, and sure enough an unusual early season disturbance came off Africa and held together to become minimal Tropical Storm Bret, which is currently scraping the coast of South America.

The western Pacific, which often spawns monster typhoons, is also above average, but there has been no activity lately. And in the eastern Pacific, the water southeast of Hawaii, so warm last year that it allowed several storms to threaten the islands, is cooler this season.

Finally, both lobes of the North Indian Ocean, particularly the Arabian Sea, are warm. Last year the water was also warmer than normal, and two record-breaking storms impacted the Arabian Peninsula.

Greenhouse Effect

Greenhouse gases absorb and trap the earth’s radiation. Graphic courtesy of NOAA.

There is still some residual resistance to the idea that human activities are causing the world to warm. Perhaps the technical explanation about the properties of carbon dioxide and methane are too complicated, so let’s try a simpler explanation.

There’s a reason for calling the effect of certain gases the Greenhouse Effect. What is a Greenhouse? It’s simply a structure made of glass. Why glass? Because sunlight passes through, is converted to heat, and is trapped. The trapping is accomplished because the glass does not conduct heat well. So the warm air inside the greenhouse cannot get out through the glass.

Now consider the atmosphere. Greenhouse gases have very little effect on sunlight, which passes through and heats the ground. The ground also emits radiation, but it is in a wavelength (microwave) which cannot pass though carbon dioxide and methane. The greenhouse gases act, in the case of the atmosphere, like the glass in a greenhouse. Greenhouse glass traps warm air; greenhouse gases trap the earth’s radiation.

There is little disagreement among scientists that greenhouse gases trap heat. There is also little doubt that a major source of atmospheric greenhouse gases is the burning of fossil fuels.

The Uncertain Future

The rate of increase in global CO2 emissions has declined in recent years, and was flat in 2015. While emissions continued to increase in developing countries, particularly India, declines in the US and China offset them in 2015. Much of the decline in the US is due to the availability of cheap natural gas, which is supplanting coal. Though cleaner than coal, natural gas is simply a bridge to a renewable-energy future. In China, the growth of GDP has slowed, and this, coupled with recent government policy changes, has led to lower emissions. Nevertheless, while emissions growth has leveled off, CO2 is still being added to the atmosphere. There is a long way to go to reach the UN’s goal of zero emissions by 2100.

Though the Paris agreement laid out a general path forward in which developed countries will convert from burning fossil fuels to using renewable energy sources while developing countries will largely skip the fossil-fuel-burning stage and go straight to renewables, the details are not clear. In particular, the detail of ‘who pays what?’ is missing.

To some extent, the problem of greenhouse gas emissions may solve itself. The cost of wind and solar power is declining. But relying on market forces cannot be the complete answer. Concerted action by governments must be part of the equation. Whether the Paris agreement is sufficient to curb greenhouse emissions enough to avert catastrophic consequences of climate change is still an open question.

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