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 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 November 2018. (To get these updates delivered right to your inbox, sign up for our Hot Science newsletter.)

Greenhouse gas emissions and temperature

  • New high for atmospheric carbon dioxide: The World Meteorological Organization’s (WMO) annual Greenhouse Gas Bulletin was released in November, and found that concentrations of carbon dioxide were at an all-time high last year: 405 parts per million (ppm), up from 403 ppm in 2016 and 400 ppm in 2015. These recent carbon dioxide levels are 50 percent greater than preindustrial levels.
  • Methane release from glacial meltwaters: Scientists have found that the Sólheimajökull glacier in Iceland is releasing 41 tonnes of methane, a greenhouse gas 28 times worse than carbon dioxide, every day in the summer as the glacier melts. Conditions at the glacier, located next to the Kayla volcano, are allowing microbes to thrive and generate methane. Importantly, Antarctica also has ice-covered, active volcanoes, so this phenomenon could occur elsewhere, leading to more emissions as the climate warms.
  • Coastal wetlands in U.S. found to be a carbon sink: For the first time, the U.S. Environmental Protection Agency, which compiles the national GHG inventory, included managed coastal wetlands in the inventory, using methodology established by the Intergovernmental Panel on Climate Change (IPCC) in 2013. U.S. coastal wetlands were found to be a net sink of GHGs in 2017, but they continue to shrink because of development, with the largest losses in the Mississippi River Delta from, among other factors, oil and gas extraction. The inclusion of wetlands has shed light on emissions reduction potential of conserving and restoring wetlands.
  • Large “emissions gap”: This month, scientists working with UN Environment program published the annual Emissions Gap Report, which found that the gap between where emissions are headed and where they need to be, is large and growing. The report also highlighted that only seven countries in the G20 (Australia, Brazil, China, EU, India, Japan and Russia) are currently on track to achieve their 2020 pledges to cut emissions.
  • 2018 likely to be fourth warmest on record: WMO recently released its State of the Climate Report, which found that the 20 warmest years on record were all within the last 22 years. Given warming to date, they expect that 2018 will be the fourth warmest on record. The past decade was 0.93˚C warmer than pre-industrial levels, with the past five years being 1.04˚C warmer.

Ocean behavior

  • Sea level rise projections too conservative: Scientists have compiled a database of 21st century global sea level rise projections and have found that the upper projections from individual studies are higher on average than the upper projections from the IPCC. They argue that the IPCC “errs on the side of least drama” and their conservative bias could get in the way of effective risk management.
  • Seabeds counter ocean acidification: Deep seabeds hold calcium carbonate which dissolves in the acidifying ocean. When this occurs, the calcium carbonate neutralizes excess carbon dioxide, acting to counter acidification. Scientists have now determined that in the western North Atlantic there is significant dissolution occurring already, which can mitigate runaway ocean acidification. The authors expect that dissolution will intensify and expand over vast areas of the seabed in the coming decades and centuries.


  • U.S. Climate Assessment documents widespread climate impacts: The Fourth National Climate Assessment Report released in late November provided a clear and strong message that climate change is already affecting every sector and region in the U.S., and further warming will wreak havoc on the nation’s health, lands and economy.
  • Intensifying hazards pose a broad threat to humanity: Scientists have found evidence for 467 different ways that climate hazards are affecting water, food, health, the economy, infrastructure and security. The authors state that greenhouse gas emissions “pose a broad threat to humanity” because they intensify multiple hazards which can simultaneously impact society.
  • Slow shift to drier forest ecosystems in the Amazon: Researchers have found that a slow shift to a drier ecosystem is underway in lowland Amazonian forests, alongside a longer and drier dry season. Newly established trees tend to be from more drought-tolerant genera, and wet-tolerant genera have increasingly died in places where the dry season has intensified. Changes in tree composition are lagging behind the rate of climate change, and the forest is not responding quickly enough to keep pace with the changes. The changes witnessed so far are indicative of future shifts in the Amazon, with significant impacts to biodiversity, and compromises to the forests’ storage of carbon.
  • Shellfish in decline: Between 1980 and 2010, there have been sharp declines (an overall 85 percent loss of commercial landings) of several species of bivalve mollusks, such as oysters, quahogs, scallops, and clams, along the East Coast of the United States. While previous studies had pointed to overfishing as the culprit, a new study found that temperature change has played an important role. Warming has made the shellfish more susceptible to predators. The decline of these species could have implications for commercial fisherman and consumers, with potential price increases for shellfish.
  • U.S. maize yields boosted by better weather: Maize yields in the U.S. have grown more than five-fold over the 20th century. While technological improvements have contributed to this boost, scientists have now documented that warmth during the growing season has also played a factor. Scientists suggest that more than one quarter of the increase in crop yields since 1981 resulted from warmer temperatures, dampening of extreme temperatures and changes to crop schedules to take advantage of such weather shifts.
  • Performance of planes affected by climate change: In a new study published this month, scientists have found that climate change could impact the performance of planes during takeoff. Increasing temperatures and changes in atmospheric pressure could require as much as 168 meters more takeoff distance in future summers for a mid-size passenger jet. These findings have implications for future aircraft design.
  • Crime rates up with mild winters: A new study finds a significant positive correlation between winter temperatures and both violent and property crime rates. There is little detectible correlation in the summertime. The authors suggest that people are more likely to be on the move when winters are milder.


  • Climate impacts to health: The Lancet released its 2018 report on health and climate change, which was put together by experts from 27 academic institutions, the United Nations and numerous intergovernmental agencies. The report finds that recent climate impacts, such as heat waves and vector-borne diseases, which have already impacting millions of people, are early warning signs of what’s to come. The authors expect that climate change will shape public health and potentially overwhelm public health services.
  • Tsetse flies in decline: In Zimbabwe, the Mana Pools National Park has witnessed declines in tsetse flies, which carry a fatal disease to humans and animals. Using a model studying 27 years of tsetse fly population and temperature data, scientists have now determined that increasing temperatures may indeed explain the collapse in tsetse abundance. The scientists conclude that in low-lying warm areas, the populations may be reduced, while in higher cooler parts of Zimbabwe new threats of tsetse could emerge as the flies move into more suitable areas.
  • Fewer premature deaths with ambitious climate action: new study quantifies the benefits to air quality from advancing climate action. For example, achieving countries’ climate commitments in their Nationally Determined Contributions could lead to 71,000 to 99,0000 fewer premature deaths from air pollution annually in 2030. If ambition is increased in line with a 2˚C pathway, 178,000 to 346,000 premature deaths from air pollution would be avoided in 2030 (and 0.7 to 1.5 million deaths avoided in 2050).

Extreme weather

  • Warming of oceans plays dominant role in 2017 hurricane activity: Researchers have now attributed the increase in major hurricane activity in the Atlantic Ocean in 2017 largely to climate change rather than to La Nina ocean conditions. The scientists posit that the warming trend will lead to more major hurricanes in the future.
  • Climate change to blame for extreme rainfall of recent hurricanes: new study finds that climate change increased the average and extreme rainfall associated with the destructive hurricanes Katrina, Irma and Maria. The authors expect a substantial future intensification of intense tropical cyclone events.
  • Summertime extreme weather to increase: A number of recent studies have found that changes in the jet stream, bands of wind in the upper atmosphere, have been associated with persistent extreme summer weather events, such as heat waves and drought. Scientists have now found that changes to the jet stream could increase by about 50 percent — and possibly larger — this century if emissions continue unabated, with significant implications for extreme weather in summer months.
  • Yield shocks from warm and dry conditions:  Scientists have found that if carbon emissions are not abated, there is a substantially greater probability of extremely warm and dry conditions occurring at the same time in key agricultural regions in China and India, which could lead to yield volatility and shocks. The probability of both warm and dry conditions happening simultaneously has doubled due to human-induced climate change.

Renewable energy

  • Future impacts to hydropower in California: Hydropower is used in California to provide grid stability when there are disruptions to electricity production, which will be in greater demand as more renewables are adopted. Using projections from four climate models for mid- and high-range warming scenarios, the researchers find that, given shifts in runoff due to climate change, there could be a net increase of water flowing into large hydropower units earlier in the year. However, this does not mean that more electricity would be generated as a result: the increased inflow could overwhelm storage, resulting in spillage. The modelers also found that long periods of drought would result in a reduction in hydropower generation, which could lead to reliance on fossil fuels to ensure grid stability.
  • Improved long-lived, safe and inexpensive batteries: Large-scale deployment of renewables in part relies on storage, given that the sun isn’t always shining and it’s not always windy. An advanced type of battery, called a flow battery, is a promising solution because it can store electricity for many hours and is made of non-toxic materials. However, scaling such batteries has been challenging to date because they are made with vanadium, an expensive, rare metal. Researchers just achieved a breakthrough by using an alternative iron-based compound to replace vanadium, that can make flow batteries long-lived and safe while also bringing costs down significantly.