This Week in Climate Science: Contrails, Chinese Nuclear Power, Mangroves etc.

By David Kroodsma

Welcome to Climate Central’s weekly climate science roundup. This roundup summarizes the noteworthy climate science articles published in the previous week, with a special emphasis on articles that might not have been covered in major media outlets.

More carbon is stored in the soils of mangrove forests than was previously believed, meaning that the destruction of mangroves is an important — and relatively unrecognized — manmade source of CO2 to the atmosphere. Credit: istockphoto

This week in climate science:

  • Why nuclear power is cheaper in China than the U.S.
  • Warm ocean currents cool eastern North America and eastern Asia during winter.
  • Jet contrails warm the climate.
  • Mangrove forests have unexpectedly high soil carbon.
  • Climate change threatens the efficacy of European biological reserves.
  • The equatorial Atlantic’s “cold tongue” has weakened during the past 60 years.
  • Why it is better to average different climate models.
  • Historic costs of coal electricity.
  • The growth of vehicles in China has been underestimated.



Paper Title: A comparison of the nuclear options for greenhouse gas mitigation in China and in the United States

Journal Title: Energy Policy

Author: C. Yang

Credit: Bret Arnett/flickr

The Gist: China can build nuclear power plants relatively cheaply because Chinese utilities are fully controlled by the state, allowing for standardization and economies of scale. 

Summary: Today, China’s nuclear power industry is booming, while the United States’ is relatively stagnant: 27 reactors are under construction in China, while the U.S. is building only one. This paper compares the nuclear industries in each country, while drawing comparisons with France’s nuclear power industry. According to Yang, the U.S. cancelled almost all orders for nuclear power in the 1970s because the cost of nuclear became too high, and because electricity demand grew more slowly than expected (the Three Mile Island incident also had a minor effect). Yang argues that one reason costs were high was that the U.S. used many different types of reactors, and thus couldn’t easily benefit from economies of scale.

By comparison, when France scaled up its nuclear industry, it built the exact same reactor model 58 times and was thus able to build each power plant more cheaply. France was able to implement such a strategy because it has a single, state-owned utility, compared to the United States’ relatively fragmented utility market. Likewise, in China, utilities are heavily controlled by the state, making coordination, standardization — and thus economies of scale — easier. In the United States, litigation and permitting hold up most new nuclear power plants.


The article concludes that the United State’s inability to implement cheap nuclear power will make it more difficult to cut carbon dioxide (CO2) emissions. Unfortunately, the article does not estimate how much more difficult it will be. 

Paper TitleWinter cold of eastern continental boundaries induced by warm ocean waters

Journal: Science

Authors: Y. Kaspi and T. Schneider

The Gist: Warm ocean currents in the North Pacific and Atlantic Oceans may be responsible for cooling eastern North America and Asia during the winter. 

Summary: Look at a world map, and you’ll notice that England is at the same latitude as Newfoundland, yet Newfoundland’s climate is frigid compared to England’s. Conventional wisdom says that this climate mismatch is because the Gulf Stream warms Western Eruope. Kaspi and Shneider, the authors of this paper, argue that the Gulf Stream is to blame, but not because it warms Europe. Instead, the warm waters create a type of atmospheric wave that pulls Arctic air into eastern North America, keeping the region much colder during winter than Western Europe. A similar phenomenon, they say, is found in the North Pacific — warm ocean currents cool eastern Asia, making the region colder than Alaska and western Canada.


A press release for this paper explains this process in more detail.

Paper Title: Climate change threatens European conservation area

Journal: Ecology Letters

Authors: M. B. Araujo, D. Alagador, M. Cabeza, D. Nogues-Bravo, and W. Thuiller

The Gist: Europe’s vast network of protected areas may not shield its biodiversity from climate change.

Summary: Europe has more than 100,000 protected areas across 54 countries. The European Union has also established the Natura 2000 network, which includes 27,661 different protected areas covering 17 percent of the EU. These protected areas are islands in a developed landscape. As the climate changes in the 21st century, some species may survive only if they can colonize new protected areas. This study used ecological and climate modeling to estimate how global warming could affect 585 different species of animals and 1,298 species of plants. The authors found that by 2080, 58 percent of species may lose suitable climates in their current protected areas. The paper recommends developing policies that will help species move between biological reserves. 

Paper Title: Global radiative forcing from contrail cirrus

Journal: Nature Climate Change

Authors: U. Burkhardt and B. Kärche

A contrail from a Boeing 777 jetliner. Credit: Fly For Fun/flickr

The Gist: Airplane contrails (condensation that forms behind high altitude jetliners) affect climate in a number of complicated ways, and may have a stronger warming effect than the CO2 emissions from the jet engines. 

Summary: Contrails (short for “condensation trails”) are created when warm, moist air exits a jet engine and is rapidly cooled by the frigid air in the upper atmosphere (one reason for the moisture is that the combustion of jet fuel produces water as well as CO2). This paper models different types of contrails and shows how they affect cloudiness and the earth’s energy balance. If the weather is favorable, some contrails persist and form cirrus-like clouds or cloud clusters, which the authors argue have a much stronger warming effect than the CO2 the planes release. Of course, the authors note that CO2 stays in the atmosphere for decades or centuries, while the contrails may disappear within hours, making CO2 emissions more of a long-term challenge in the end.

Paper TitleMangroves among the most carbon-rich forests in the tropics

Journal: Nature Geoscience

Authors: D. C. Donato, J. Boone Kauffman, D. Murdiyarso, S. Kurnianto, M. Stidham, and M. Kanninen

The Gist: More carbon is stored in the soils of mangrove forests than was previously believed, meaning that the destruction of mangroves is an important — and relatively unrecognized — manmade source of CO2 to the atmosphere.

Summary: This study analyzes soils in 25 mangrove forests across the globe, finding that mangroves have some of the highest levels of soil carbon in the tropics. The ecosystems store about five to ten times as much carbon in the roots and soils than they do in the above-water biomass. Unfortunately, mangroves are being rapidly cut down and removed, and 30 to 50 percent of the world’s mangroves have already been eliminated. The authors estimate that the yearly deforestation of mangroves contributes up to 10 percent of the global CO2 emissions from deforestation.


Paper TitleWeakening of the equatorial Atlantic cold tongue over the past six decades

Journal: Nature Geoscience

Authors: H. Tokinaga and S. Xie

The Gist: Ship data shows that the Atlantic “cold tongue,” a phenomenon in the equatorial Atlantic, has weakened over the past 60 years, possibly due to increased aerosols in the atmosphere.

Summary: Each year, between April and July, a “cold tongue” of surface water forms in the equatorial Atlantic, protruding from Africa toward the central Atlantic. This study analyzes 60 years of data from ships and finds that the strength of this “cold tongue”— the difference between the water temperature near Africa and the water temperature near South America — has decreased. Ship records also show that the equatorial trade winds in the eastern portion of the Atlantic Ocean have weakened, which the authors say is consistent with a weaker cold tongue. The authors speculate that the decrease in this phenomenon may be due to increased atmospheric aerosols.

Paper TitleHistoric costs of coal-fired electricity and implications for the future

Journal:  Energy Policy

Authors: J. McNerney, J. D. Farmer, J. E. Trancik

The Gist: Historically, the cost of building coal-fired power plants in the U.S. has decreased, then increased, and then reached a plateau; the cost of coal, on the other hand, has fluctuated randomly.

Summary: The authors study the cost of coal-generated electricity in the United States between 1982 and 2006. They find that the price of coal has fluctuated somewhat randomly over that period, while the construction cost of power plants have followed a clear trend: they decreased in cost from 1902 to1970, increased in cost from 1970 to 1990, and then leveled off. The authors conclude that even if the price of building power plants decreases, the future price won’t be possible to reliably predict because of the fluctuation of coal prices.

Paper Title: China’s soaring vehicle population: Even greater than forecasted?

Journal:  Energy Policy

Authors: Y. Wang, J. Teter, D. Sperling

The Gist: Most studies vastly underestimate the growth of China’s vehicle fleet.

Summary: The number of cars and trucks in China is growing rapidly, but how rapidly? Most experts have estimated that the number of vehicles in China will increase by between six and 11 percent per year for the foreseeable future. The authors of this study argue that these numbers are vast underestimates; barring an economic collapse, the number of vehicles in China will increase at perhaps twice that rate — between 13 and 17 percent during the next decade. The authors also analyze historic growth rates in other countries when those countries were at a similar level of Gross Domestic Product (GDP) per person as China is today.


If the authors are correct, over the next ten years the number of vehicles in China will grow from today’s 80 million vehicles to perhaps as many as 385 million. If that’s the case, projections of petroleum use — and greenhouse gas emissions — may need to be revised upwards.