The greenhouse gas emissions reported by the UNFCCC are inaccurate; emissions may be slightly higher, meaning that the world is even more likely to warm by more than 2° Celsius by the end of this century.
At the United Nations Framework Convention on Climate Change (UNFCCC) negotiations in Copenhagen, Denmark in 2009, world leaders set a goal of keeping global warming under 2°C, compared to preindustrial levels.
However, according to several analyses, countries have not yet pledged sufficient emissions reductions
to meet that target. There is a “gap” between what is needed to keep warming to at or below the 2°C target, and what has been pledged. The authors of this study argue that previous studies of the “gap” have used the official greenhouse gas emissions as reported by the UNFCCC, and these numbers may underestimate actual annual emissions by a few percent. That means that the gap is even larger than previously thought.
The paper also summarizes the previous studies, all of which show that current pledges almost certainly put us on track to exceed 2°C of warming.
The Gist: Putting reflective aerosols high into the atmosphere to slow climate change is too risky and not cost effective.
Summary: Some have argued that if human society cannot sufficiently reduce its greenhouse gas emissions, than we could still avoid the worst consequences of global warming by putting highly reflective particles, known as aerosols, high into the atmosphere. These aerosols would reflect light back to space, thus counteracting warming from greenhouse gases.
The authors of this paper use an integrated assessment model to determine how costly such a method would be. The authors discuss the potential side effects of this so-called “geoengineering” strategy, since adding aerosols to the atmosphere could have unintended consequences, such as significantly altering weather patterns and damaging stratospheric ozone. Also, aerosols are short-lived, and would have to be continuously added to the atmosphere in order for this scheme to work. If society stopped injecting them, the result would be a rapid shift in the climate, something this paper argues would be highly damaging.
The authors calculate that if there is greater than a 15 percent chance that such a method will be shut down, or if the unintended consequences of aerosols are greater than half a percent of the world’s economy, then this method of geoengineering is not worth the effort.
The Gist: When large icebergs capsize and flip, they can release enough energy to create a small tsunami.
Summary: When an iceberg is taller than it is wide, it is unstable and can flip onto its side. The authors estimate that when this happens, it can release enough energy to create a tsunami that is up to one percent the height of the iceberg. For an average Antarctic iceberg, which is about 1,300 feet tall, that corresponds to a 13-foot tsunami. The world’s tallest icebergs can be over 3,000 feet tall, which could, according to this calculation, create a tsunami more than 30 feet tall. Such waves have been known to affect communities in Greenland, but the study doesn’t speculate whether climate change will create more of these waves.
The study also doesn’t speculate on the risk the icebergs pose to human settlements, most of which are far from Antarctica, where the largest icebergs and waves would be created. This paper was also summarized in a recent news article in Nature.
A Series of Letters Debating a Paper on Tibetan Spring
Springtime in Tibet. Credit: Jerrold/flickr.
The Gist: Scientists debate why the Tibetan spring is not coming earlier.
Summary: In August of last year, the scientists Haiying Yu, Eike Luedeling, and Jianchu Xu published a paper in PNAS that argued that warmer winters in Tibet were — contrary to conventional thinking —actually delaying the Tibetan spring. They argued that some plants needed many days of cold before being ready for spring, and in Tibet they were not getting enough cold days during winter. In the most recent issue of PNAS, three other groups of scientists published letters critiquing this study, and in response, Yu and her colleagues published a third letter defending their original study. The first letter argues that factors such as grassland degradation or changes in the freeze-thaw patterns could be driving the change in springtime. A second letter argues that the original findings were not statistically significant. A third letter argues that the culprit might be increased air pollution, not winter temperatures. In the final letter, the original authors defend their paper and respond to the critiques.
This exchange is a good example of science in action: one group of scientists make a claim, and another group challenges it.
The Gist: The recent warming of continental West Antarctica is likely due to warmer sea surface temperatures in the tropical Pacific.
Summary: The portion of Antarctica that faces the Pacific, known as West Antarctica, has warmed significantly during the past 30 years. While the warming on the Antarctic Peninsula has been explained by changes in the winds that circle Antarctica, the warming on the continent has been greater than expected by climate scientists.
The authors of this study argue that warming is a result of conditions far across the ocean. Warm temperatures in the tropical Pacific has induced a stationary wave in the atmosphere known as a Rossby wave, the researchers report. This wave influences atmospheric circulation off the coast of Antarctica and causes more warm air to reach the continent.
The Gist: The drought of 2010 in the Amazon basin was more severe and covered a larger area than the drought of 2005, and represents a potentially significant change in the global carbon cycle.
Summary: In 2005, a major drought affected the Amazon basin, and was considered to be one of the worst on record — a “once-in-a-century” event. Then, in 2010, an even more severe drought struck. This paper compares the 2010 drought to the 2005 event, and finds that the 2010 drought affected an area more than fifty percent larger than the 2005 drought, and that river levels in the Amazon and its tributaries were the lowest on record.
Understanding Amazonian droughts is important because some climate models show that global warming may make large portions of the Amazon basin too dry for the current rainforest to survive. If these models are correct, grasslands will replace forests across large portions of the basin. This means that the carbon dioxide (CO2) that is currently stored in the biomass of the forest would be released to the atmosphere, amplifying global warming. The authors of this study, while mentioning the possibility of “Amazon die-back,” don't speculate on whether the 2010 drought is the beginning of such a phenomenon.
The Gist: If boreal forests expand northward, climate models show that summers will warm because the forests will absorb more heat than the surrounding tundra.
Summary: Stefan Liess and his colleagues estimate how an expanding boreal forest could affect the climate in the Far North. They find that forest expansion could increase global warming because the trees are darker than the tundra, and thus absorb more solar energy. They find that if boreal forest replaces tundra, the Arctic summer could warm by one to two degrees Celsius more than expected.
The Gist: The “greenness” of the boreal and temperate forests of Eurasia increased between 1982 and 1997 and then decreased from 1997 and 2006.
Summary: Using satellite data, the authors analyzed the greenness of Eurasia’s boreal and temperate forests from 1982 to 2006. Understanding how ecosystems respond on a continental scale is important for understanding the earth’s natural carbon cycle.
The authors suggest that the greenness increased between 1982 and 1997 because of warming temperatures, and that it decreased after 1997 because of a drying trend in the region. The authors do not speculate on future trends on the continent. Another study, reported on by Climate Central, further discusses the ecosystems in the Far north, which are undergoing rapid change.
The Gist: The technical know-how for Carbon Capture and Storage (CCS), a technology that removes CO2 from the exhaust of power plants, needs to be transferred from developed to developing nations.
Summary: Carbon Capture and Storage (CCS) is a technology that removes CO2 from the exhaust of coal and gas power plants and then pumps the waste CO2 underground so that it does not enter the atmosphere. The technology is only now being developed, and is still quite costly. It is being developed mostly in research centers and by companies in wealthy nations. However, developing nations plan to build the most fossil fuel power plants in the coming decades, and will need this technology.
This paper looks at policies that could promote the transfer of CCS technology from wealthy nations to developing ones.
The Gist: The public debate over nuclear power varies greatly between Finland, France, and the UK.
Summary: Many countries have seen a resurgence of interest in nuclear power because the technology produces almost no greenhouse gas emissions. France, Finland, and the UK are all planning or building new nuclear power plants. All three countries generate significant portions of their electricity from nuclear power (UK: 18 percent, Finland: 33 percent, France: 75 percent), yet few nuclear power plants have been built in these countries during the past two decades.
This paper analyzes the public debate in each of these countries, finding that Finland’s debate focuses on technology, the U.K.’s on economics, and France’s on the role and reliability of government.
The Gist: The European Commission’s banning of incandescent light bulbs is economically inefficient.
Summary: Starting in 2009, the European Commission began a gradual phase-out of incandescent bulbs, and beginning in 2012, only energy-efficient bulbs, such as compact fluorescents or L.E.D.’s will be commercially available. Because newer bulbs are several times more efficient than incandescent ones, the European Commission argued that this phase out will both save consumers money and reduce CO2 emissions. According to this paper, most previous studies agree that energy-efficient bulbs are far better for consumers.
This paper argues that in cases where a bulb is infrequently used, such as in an attic or basement, the cheaper incandescents are a better economic choice. The authors also argue that such laws infringe on the right of customers to make their own decisions.