A Journal of People report
Winter days where temperatures peak above 14 degrees Fahrenheit (minus 10 degrees Celsius) are considered as Arctic winter warming event. Arctic winter warming events are a normal part of the climate over the ice-covered Arctic Ocean, but these were not as frequent as now and were not lasting longer.
An international team that includes NASA scientists finds Arctic winter warming events are becoming more frequent and lasting longer than they did three decades ago.
At the same time, a monthly analysis of global temperatures by scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York finds June 2017 was the fourth warmest June in 137 years of modern record-keeping.
Monthly analysis of global temperatures by scientists at NASA’s GISS has also found May 2017 was the second-warmest May in 137 years of modern record-keeping.
Arctic winter warming events
Kelsey Simpkins of American Geophysical Union wrote:
During fall and winter Arctic sea ice grows and thickens. But warmer winter air temperatures will further impede ice growth and expansion, accelerating the effects of global warming in the Arctic.
By adapting Kelsey Simpkins’ report, Maria-Jose Viñas of NASA’s Earth Science News Team wrote on July 11, 2017:
“A new study, published in Geophysical Research Letters on July 10, shows that since 1980, an additional six warming events are occurring each winter in the North Pole region. The study also shows the average length of each event has grown from fewer than two days to nearly two and a half days.”
The report headlined “Arctic winter warming events becoming more frequent, longer-lasting” in NASA’s Global Climate Change said:
“The researchers arrived at the results by gathering and analyzing data from field campaigns, drifting weather stations and buoys across the Arctic Ocean from 1893 to 2017, as well as the ERA-Interim record, a global atmospheric reanalysis provided by the European Centre for Medium-Range Weather Forecasts in Reading, UK, from 1979 to 2016.
“The findings build on other recent evidence of Arctic winter warming. The winter of 2015-2016, for example, saw temperatures nearly 3.6 degrees Fahrenheit (2 degrees Celsius) warmer than the previous record high monthly winter temperature. At the end of December 2015, scientists recorded a temperature of 36 degrees Fahrenheit (2.2 degrees Celsius) in the Central Arctic, the warmest temperature ever recorded in this region from December through March.
“In the most recent years of the study, each warming event was associated with a major storm entering the region. During these storms, strong winds from the south blow warm, moist air from the Atlantic into the Arctic.”
“The warming events and storms are in effect one and the same,” said Robert Graham, a climate scientist at the Norwegian Polar Institute in Tromsø, Norway, and lead author of the new study. “The more storms we have, the more warming events, the more days with temperatures less than minus 10 degrees Celsius (14 degrees Fahrenheit) rather than below minus 30 degrees Celsius (minus 22 degrees Fahrenheit), and the warmer the mean winter temperature is.”
The Global Climate Change report said:
“Storms that bring warm air to the Arctic not only prevent new ice from forming, but can also break up ice cover that is already present, Graham said. He added that the snowfall from storms also insulates current ice from the cold atmosphere that returns to the Arctic after the cyclones, which can further reduce ice growth.
“Two of the study’s authors, Alek Petty and Linette Boisvert of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, previously researched one such storm that took place in the Arctic during the winter of 2015-2016.”
“That particular cyclone, which lasted several days and raised temperatures in the region close to the melting point, hindered sea ice growth while its associated strong winds pushed the sea ice edge back, leading to a record low spring sea ice pack in 2016,” said Petty and Boisvert. “This new study provides the long-term context we were missing, using direct observations going back the end of the 19th century. It shows that these warm events have occurred in the past, but they were not as long-lasting or frequent as we’re seeing now. That, combined with the weakened sea ice pack, means that winter storms in the Arctic are having a larger impact on the Arctic climate system.”
The report said:
“The next step for Graham and his colleagues is to understand what is fueling the increase of these storms and how they might change. Recent research shows that reduced ice cover and shifting weather patterns due to climate change may increase storms’ frequency and impact, Graham said. ‘It is difficult to say how much this pattern will amplify in the future,’ he said.”
A report by NASA’s GISS/Global Climate Change said on July 14, 2017:
“Last month was 0.69 degrees Celsius warmer than the mean June temperature from 1951-1980. It is surpassed by June 2016 (+0.79 °C) and June 2015 and 1998 (+0.78 °C) and only insignificantly warmer than June 2005 (+0.68 °C).”
The “June 2017 was fourth-warmest on record” headlined report said:
“Except for June 1998, the 10 warmest months of June occurred between 2005 and 2017.
“The monthly analysis by the GISS team is assembled from publicly available data acquired by about 6,300 meteorological stations around the world, ship- and buoy-based instruments measuring sea surface temperature, and Antarctic research stations.
“The modern global temperature record begins around 1880 because previous observations didn’t cover enough of the planet. Monthly analyses are sometimes updated when additional data becomes available, and the results are subject to change.”
Another report from NASA’s GISS/Global Climate Change said on June 15, 2017:
“May 2017 was the second-warmest May in 137 years of modern record-keeping, according to a monthly analysis of global temperatures by scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York.”
The “May 2017 was second-warmest May on record” headlined report said:
“May 2017 was 0.88 degrees Celsius warmer than the mean May temperature from 1951-1980. The two top May temperature anomalies have occurred during the past two years. 2016 was the hottest on record, at 0.93 degrees Celsius warmer than the May mean temperature.
“May 2017’s temperature was 0.05 degrees Celsius cooler than May 2016. It was just 0.01 degrees Celsius warmer than the third warmest May, which occurred in 2014.
“The monthly analysis by the GISS team is assembled from publicly available data acquired by about 6,300 meteorological stations around the world, ship- and buoy-based instruments measuring sea surface temperature, and Antarctic research stations.”
A rainier future
Carol Rasmussen of NASA’s Jet Propulsion Laboratory writes in NASA’s Global Climate Change on June 9, 2017:
“A new study suggests that most global climate models may underestimate the amount of rain that will fall in Earth’s tropical regions as our planet continues to warm. That’s because these models underestimate decreases in high clouds over the tropics seen in recent NASA observations, according to research led by scientist Hui Su of NASA’s Jet Propulsion Laboratory in Pasadena, California.”
The “NASA data suggest future may be rainier than expected” headlined report said:
“Globally, rainfall isn’t related just to the clouds that are available to make rain but also to Earth’s ‘energy budget’ — incoming energy from the sun compared to outgoing heat energy. High-altitude tropical clouds trap heat in the atmosphere. If there are fewer of these clouds in the future, the tropical atmosphere will cool. Judging from observed changes in clouds over recent decades, it appears that the atmosphere would create fewer high clouds in response to surface warming. It would also increase tropical rainfall, which would warm the air to balance the cooling from the high cloud shrinkage.
“Rainfall warming the air also sounds counterintuitive — people are used to rain cooling the air around them, not warming it. Several miles up in the atmosphere, however, a different process prevails. When water evaporates into water vapor here on Earth’s surface and rises into the atmosphere, it carries with it the heat energy that made it evaporate. In the cold upper atmosphere, when the water vapor condenses into liquid droplets or ice particles, it releases its heat and warms the atmosphere.
“The new study is published in the journal Nature Communications. It puts the decrease in high tropical cloud cover in context as one result of a planet-wide shift in large-scale air flows that is occurring as Earth’s surface temperature warms. These large-scale flows are called the atmospheric general circulation, and they include a wide zone of rising air centered on the equator. Observations over the last 30 to 40 years have shown that this zone is narrowing as the climate warms, causing the decrease in high clouds.”
The study is titled “Tightening of Tropical Ascent and High Clouds Key to Precipitation Change in a Warmer Climate.”
The report said:
“Su and colleagues at JPL and four universities compared climate data from the past few decades with 23 climate model simulations of the same period. Climate modelers use retrospective simulations like these to check how well their numerical models are able to reproduce observations. For data, the team used observations of outgoing thermal radiation from NASA’s spaceborne Clouds and the Earth’s Radiant Energy System (CERES) and other satellite instruments, as well as ground-level observations.
“Su’s team found that most of the climate models underestimated the rate of increase in precipitation for each degree of surface warming that has occurred in recent decades. The models that came closest to matching observations of clouds in the present-day climate showed a greater precipitation increase for the future than the other models.
“Su said that by tracing the underestimation problem back to the models’ deficiencies in representing tropical high clouds and the atmospheric general circulation, ‘This study provides a pathway for improving predictions of future precipitation change.’”