Every month, climate scientists make new discoveries that advance our understanding of climate change’s causes and impacts. The research gives a clearer picture of the threats we already face, and explores what’s to come if we don’t reduce emissions at a quicker pace.
Our new blog series, This Month in Climate Science, offers a snapshot of the month’s significant scientific literature, compiled from some of the leading peer-reviewed journals. This edition explores studies published in June 2018. While it is not meant to be comprehensive, it provides an overview of the latest scientific revelations, including overlooked problems and potential solutions. (To get these updates delivered right to your inbox, sign up for our Hot Science newsletter.)
Antarctic melt speeding up: Reporting in Nature, 80 scientists found that the melting of Antarctica is speeding up. They compared 24 independently derived estimates of the Antarctic Ice Sheet’s mass and found that it has lost about 2,720 billion tonnes between 1992 and 2017. The picture in West Antarctica is the clearest. Ice loss there has roughly tripled, from 53 billion tonnes per year to 159 billion tonnes per year over the same time period.
But in East Antarctica, the picture is more ambiguous. While most scientists believe East Antarctica is on average gaining mass in the form of ice and snowfall, or both, they also believe that increases in the East are not enough to offset losses in the West. The continent is losing ice mass overall.
To further complicate the picture, scientists reported in Science new information on the upward movement of Antarctica’s underlying bedrock, which could suggest the Ice Sheet is more stable than previously thought. The Earth's crust deforms when it is under the weight of glaciers and ice sheets. With the removal of these masses, the crust will rebound, which may help prevent the complete collapse of the West Antarctic Ice Sheet, even with significant warming. New GPS measurements signal that as ice is lost, the Earth’s crust under the West Antarctic Ice Sheet is rebounding much faster than previously expected. This surprising finding, though, may cause estimates of total ice mass loss to be revised upward by as much as 10 percent.
Extreme Events and Climate Variability
Storms moving more slowly, wreaking havoc: A study in Nature showed that storms are moving more slowly in the summer than they used to, sticking around and causing more damage, just as Hurricane Harvey did when it stalled over Texas. This is due to a weakening of summertime tropical circulation, which has been linked to human-induced warming. From 1949 to 2016, the speed of tropical cyclones declined by 10 percent globally.
Record high-tide flooding days in US: The National Oceanic and Atmospheric Administration (NOAA) found a record number of high-tide flooding days in 2017, with more than a quarter of coastal locations tying or breaking records. Cities with the highest number of flood days include Atlantic City, New Jersey; Sandy Hook, New Jersey; Boston; Galveston; Texas and Sabine Pass, Texas. NOAA suggests that 2018 may be even worse, with as much as 60 percent more high-tide flooding than 20 years ago.
Extreme events linked more to CO2 concentrations than temperature: Research in Nature Climate Changeshowed that extreme events are directly impacted by higher carbon dioxide concentrations, with an even more predictable relationship than with global temperature increase. They suggest we need explicit targets to limit CO2 concentrations, in addition to goals that limit temperature rise.
Warmer, saltier Atlantic water entering Arctic: The Barents Sea, located between the Arctic and Atlantic Oceans, is made up of a colder northern area and a warmer southern area. The waters of the northern Barents are more stratified, with freshwater at the top due to melting sea ice, and denser, saltier waters beneath. Less freshwater sea ice floating from northern latitudes means the water is becoming saltier. Publishing their results in Nature Climate Change, scientists found an “Atlantification” has occurred, leading to warming and increased salinity in the northern Barents Sea. This can reduce the area where sea ice forms and can change ecosystems, with unknown impacts on species composition and fisheries.
Human activity drives ocean acidification since Industrial Revolution: Accurate measurements of historical ocean pH are nearly non-existent, aside from limited ship track measurements and station base instrument records of the past few decades. In a new Naturearticle, scientists used coral skeletons in the South Pacific and documented evidence of uninterrupted ocean acidification since the Industrial Revolution. They showed a pronounced variability of pH in the South Pacific from 1689 to 1881, and that surface wind strength and other processes were the main drivers. But after this time, human-induced CO2 played the prominent role in driving ocean acidification, which is responsible for coral bleaching and death.
Greenhouse Gas Emissions
Carbon dioxide levels reach new milestone: May 2018 saw the highest monthly average of carbon dioxide levels since record-keeping began, reaching 411 parts per million (ppm). In 2016 and 2017, concentrations of global CO2 increased 2.3 ppm per year, in contrast with 1.5 ppm per year in the 1990s.
New carbon budget calculations for 1.5°C: There’s been recent debate about the world’s remaining “carbon budget,” the amount of carbon dioxide we can emit and still limit temperature rise to a certain amount. Using a simplified calculation based on the level and rate of warming to date, scientists calculated the world’s carbon budget for 1.5°C above pre-industrial levels. Reporting in Nature Geoscience, they found that we would burn through the budget in just 22 years at our current emissions levels. If the contribution of non-CO2 gases change, or if past warming is calculated to be higher, the budget would shrink.
Sensitive regions still at risk with warming of 1.5°C: In an article in Nature Climate Change, researchers found that even if warming is limited to 1.5°C (2.7°F), a goal laid out in the international Paris Agreement on climate change, some sensitive regions like the Arctic could still be significantly impacted by climate change. Interestingly, in 50 percent of their simulations, researchers found the world could limit warming to 1.5 degrees C without negative emissions.
Arctic archeological artifacts under threat: The Arctic’s cold, wet conditions have left archeological treasures and ecological records remarkably well-preserved. However, as reported in the journal Antiquity, scientists found that coastal erosion, permafrost thaw, increased vegetation and tundra fires are now threatening these archeological sites, such as those documenting Siberian, Greenlandic and Norwegian communities.
Coral reefs impacted by sea level rise: Reporting in Nature, scientists studied more than 200 reefs in the Caribbean and Indian Oceans and found that corals will not be able to keep pace with projected levels of sea level rise. Even under more conservative projections, most corals are not able to grow vertically quickly enough, and would be too submerged to continue growing to compensate for the rising seas, exposing coastlines to flooding and erosion.
Some of the oldest trees on Earth died, perhaps due to climate change: Baobabs are the biggest and longest-living flowering plants. Scientists reported in Nature Plants that over the last dozen years, nine of the 13 oldest and five of the six largest baobabs have died or almost died. Some of the trees date back more than 2,500 years. While the cause is unclear, the lead author suspects the combination of unprecedented high temperatures and extreme drought.
Fish on the move: In Science, researchers reported that by the end of the century, climate change will likely cause many of the world’s Exclusive Economic Zones (EEZs) to get one to five new transboundary stocks of fish. With high rates of warming, about 35 percent of global EEZs would have new transboundary stocks by end of the century; under lower rates of warming, this falls to about a quarter of EEZs. The tropics are especially hit hard, with fisheries moving out, not in. This could lead to strained maritime relations due to disputed territories, overlapping fishery claims and illegal fishing.
Species under threat: Scientists reportded in the Proceedings of the Royal Societythat by 2070, climate change will either match or exceed the effects of land use change on biodiversity. The combined impacts are projected to lead to losses of about 38 percent of vertebrates.
Fossil fuels may create trillions of dollars in stranded assets: Driven by massive declines in coal, overall fossil fuel use in U.S. electric generation fell to the lowest level since 1994, according to the Energy Information Administration. Should this trend continue, numerous investments in fossil fuel ventures could become stranded. Reporting in Nature Climate Change, analysts found that some amount of stranded fossil fuel assets will occur regardless as a result of technological progress, irrespective of new climate policies. But if countries collectively limit warming to 2 °C (3.6°F) and/or if low-cost fossil fuel producers continue their level of production despite demand reductions, stranded fossil fuel assets could cause a $1–4 trillion loss in wealth globally.
Clear solar cells: Three-quarters of U.S. electricity use is from houses and office buildings. While engineers have attempted to install solar cells in windows, they have not been fully embraced in part because of their red or brown tints. As reported in Science, a new technological development allows for solar windows to be fully transparent, enabling greater market acceptance.
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