As we begin to clean up from Hurricane Harvey, the wettest hurricane on record, dumping up to 50 inches of rain on Houston in three days, and await landfall of Irma, the most powerful hurricane on record in the open Atlantic Ocean, people are asking: What is the role of human-induced climate change in these events, and how else have our own actions increased our risks?…
By Michael E. Mann, Susan J. Hassol and Thomas C. Peterson
….Hurricanes get their energy from warm ocean waters, and the oceans are warming because of the human-caused buildup of heat-trapping gases in the atmosphere, primarily from the burning of coal, oil and gas. The strongest hurricanes have gotten stronger because of global warming. Over the past two years, we have witnessed the most intense hurricanes on record for the globe, both hemispheres, the Pacific and now, with Irma, the Atlantic.
We also know that warmer air holds more moisture, and the amount of water vapor in the atmosphere has increased because of human-induced global warming. We’ve measured this increase, and it has been unequivocally attributed to human-caused warming. That extra moisture causes heavier rainfall, which has also been observed and attributed to our influence on climate. We know that rainfall rates in hurricanes are expected to increase in a warmer world, and now we’re living that reality….\
…Cutting-edge climate science suggests that such stalled weather patterns could result from a slowed jet stream, itself a consequence — through principles of atmospheric science — of the accelerated warming of the Arctic. This is a reminder of how climate changes in far-off regions such as the North Pole can have very real effects on extreme weather faced here in the Lower 48.
These linkages are preliminary, and scientists are still actively studying them. But they are a reminder that surprises may be in store — and not welcome ones — when it comes to the unfolding effects of climate change….
Even if all fossil fuel emissions are eradicated, if current rates of deforestation in the tropics continue through to 2100 then there will still be a 1.5 degree Celsius increase in global temperature
While carbon dioxide emissions from energy use must be the primary target of climate change mitigation efforts, land use and land cover change (LULCC) also represent an important source of climate forcing.
Tackling deforestation should be higher on the climate change agenda.
In the fight against climate change, much of the focus rests on reducing our dependence on fossil fuels and developing alternative energy sources. However, the results of a new study suggest that far more attention should be paid to deforestation and how the land is used subsequently – the effects of which make a bigger contribution to climate change than previously thought.
The research, conducted by Cornell University and published in the journal Environmental Research Letters,shows just how much this impact has been underestimated. Even if all fossil fuel emissions are eradicated, if current rates of deforestation in the tropics continue through to 2100 then there will still be a 1.5 degree Celsius increase in global temperature….
Abstract: While carbon dioxide emissions from energy use must be the primary target of climate change mitigation efforts, land use and land cover change (LULCC) also represent an important source of climate forcing. In this study we compute time series of global surface temperature change separately for LULCC and non-LULCC sources (primarily fossil fuel burning), and show that because of the extra warming associated with the co-emission of methane and nitrous oxide with LULCC carbon dioxide emissions, and a co-emission of cooling aerosols with non-LULCC emissions of carbon dioxide, the linear relationship between cumulative carbon dioxide emissions and temperature has a two-fold higher slope for LULCC than for non-LULCC activities. Moreover, projections used in the Intergovernmental Panel on Climate Change (IPCC) for the rate of tropical land conversion in the future are relatively low compared to contemporary observations, suggesting that the future projections of land conversion used in the IPCC may underestimate potential impacts of LULCC. By including a “business as usual” future LULCC scenario for tropical deforestation, we find that even if all non-LULCC emissions are switched off in 2015, it is likely that 1.5°C of warming relative to the preindustrial era will occur by 2100. Thus, policies to reduce LULCC emissions must remain a high priority if we are to achieve the low to medium temperature change targets proposed as a part of the Paris Agreement. Future studies using integrated assessment models and other climate simulations should include more realistic deforestation rates and the integration of policy that would reduce LULCC emissions.
Over the next few decades, global warming-related rises in winter temperatures could significantly extend the range of the southern pine beetle — one of the world’s most aggressive tree-killing insects — through much of the northern United States and southern Canada, says a new study. The beetle’s range is sharply limited by annual extreme temperature lows, but these lows are rising much faster than average temperatures — a trend that will probably drive the beetles’ spread, say the authors. The study was published today in the journal Nature Climate Change.
…Until recently, southern pine beetles lived from Central America up into the southeastern United States, but in the past decade or so they have also begun appearing in parts of the Northeast and New England…
…”We could see loss of biodiversity and iconic regional forests. There would be damage to tourism and forestry industries in already struggling rural areas.” Coauthor Radley Horton, a researcher at Columbia University’s Lamont-Doherty Earth Observatory, said infested forests could also dry out and burn, endangering property and emitting large amounts of carbon into the atmosphere…
Corey Lesk, Ethan Coffel, Anthony W. D’Amato, Kevin Dodds, Radley Horton. Threats to North American forests from southern pine beetle with warming winters. Nature Climate Change, 2017; DOI: 10.1038/nclimate3375
July 2017 was statistically tied with July 2016 as the warmest July in the 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.
Last month was about 0.83 degrees Celsius warmer than the mean July temperature of the 1951-1980 period. Only July 2016 showed a similarly high temperature (0.82 °C), all previous months of July were more than a tenth of a degree cooler.
Starting with this update, the previously used ocean data set ERSST v4 was replaced by the newer ERSST v5. This contributed to the changes of some of the data in last month’s update. For more information, see the Updates to Analysis and the History Pages.
A global map of the June 2017 LOTI (land-ocean temperature index) anomaly, relative to the 1951-1980 June average. View larger image.
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.
….Temperature records were first broken in 2014, when that year became the hottest year since global temperature records began in 1880. These temperatures were then surpassed in 2015 and 2016, making last year the hottest year ever recorded. In 2016, the average global temperature across land and ocean surface areas was 0.94 degrees Celsius (1.69 degrees Fahrenheit) above the 20th century average of 13.9 degrees Celsius (57.0 degrees Fahrenheit), according to NOAA.
Combining historical temperature data and state-of-the-art climate model simulations, the new study finds the likelihood of experiencing consecutive record-breaking global temperatures from 2014 to 2016 without the effects of human-caused climate change is no greater than 0.03 percent and the likelihood of three consecutive record-breaking years happening any time since 2000 is no more than 0.7 percent.
When anthropogenic warming is considered, the likelihood of three consecutive record-breaking years happening any time since 2000 rises to as high as 50 percent, according to the new study…
Michael E. Mann, Sonya K. Miller, Stefan Rahmstorf, Byron A. Steinman, Martin Tingley. Record Temperature Streak Bears Anthropogenic Fingerprint. Geophysical Research Letters, 2017; DOI: 10.1002/2017GL074056
…the combinations of [high heat and humidity will] leave ever more people exposed to significant health risks, especially in East Asia and America’s East Coast.
Warm air combined with high humidity can be very dangerous as it prevents the human body from cooling down through sweating, leading to hyperthermia. As a result, if global warming trends continue, many more people are expected to suffer sun strokes, especially in densely populated areas of India, China and the US….
…the effect of relative humidity on heatwaves’ magnitude and peak might be underestimated in current research. The results of the study support the need for urgent mitigation and adaptation action to address the impacts of heatwaves, and indicate regions where new adaptation measures might be necessary to cope with heat stress.
Simone Russo, Jana Sillmann, Andreas Sterl. Humid heat waves at different warming levels. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-07536-7
A draft report by scientists from 13 federal agencies, which has not yet been made public but was obtained by The New York Times, concludes that Americans are feeling the effects of climate change right now.
Evidence for a changing climate abounds, from the top of the atmosphere to the depths of the oceans
Scientists fear Administration will dismiss or suppress the most comprehensive climate report
The report was completed this year and is part of the National Climate Assessment, which is congressionally mandated every four years.
WASHINGTON — The average temperature in the United States has risen rapidly and drastically since 1980, and recent decades have been the warmest of the past 1,500 years, according to a sweeping federal climate change report awaiting approval by the Trump administration.
The draft report by scientists from 13 federal agencies, which has not yet been made public, concludes that Americans are feeling the effects of climate change right now. It directly contradicts claims by President Trump and members of his cabinet who say that the human contribution to climate change is uncertain, and that the ability to predict the effects is limited.
“Evidence for a changing climate abounds, from the top of the atmosphere to the depths of the oceans,” a draft of the report states. A copy of it was obtained by The New York Times.
The authors note that thousands of studies, conducted by tens of thousands of scientists, have documented climate changes on land and in the air. “Many lines of evidence demonstrate that human activities, especially emissions of greenhouse (heat-trapping) gases, are primarily responsible for recent observed climate change,” they wrote.
The report was completed this year and is a special science section of the National Climate Assessment, which is congressionally mandated every four years. The National Academy of Sciences has signed off on the draft report, and the authors are awaiting permission from the Trump administration to release it.
One government scientist who worked on the report, Katharine Hayhoe, a professor of political science at Texas Tech University, called the conclusions among “the most comprehensive climate science reports” to be published. Another scientist involved in the process, who spoke to The New York Times on the condition of anonymity, said he and others were concerned that it would be suppressed….
The July average temperature for the contiguous U.S. was 75.7°F, 2.1°F above the 20th century average and was the 10th warmest July in 123 years of record-keeping. Much-above-average temperatures were observed across the West and parts of the Mid-Atlantic and Southeast. The year-to-date (January-July) average temperature for the contiguous U.S. was 54.5°F, 3.2°F above average and second warmest on record. This was slightly warmer than the same period in 2006 and 1.2°F cooler than the record set in 2012.
…Above-average temperature spanned the nation for the first seven months of 2017 with only parts of the Northwest cooler than average. Much-above-average temperatures were observed for most locations in the Southwest and from the Rockies to the East Coast, mostly due to record and near-record warmth early in the year. Florida, North Carolina and South Carolina had their warmest January-July on record.
…According to the August 1 U.S. Drought Monitor report, 11.8 percent of the contiguous U.S. was in drought, up about 3.7 percent compared to the end of June. Drought improved across parts of the Southwest, southern High Plains and in the Washington, DC, area. Drought intensified and expanded in the Northwest, Northern Rockies and Central to Northern Plains driven by below-average precipitation and above-average temperatures. The drought and heat decimated crops in the Northern Plains. Drought and abnormally dry conditions developed in parts of the Southeast and northern Maine. Drought continued to impact parts of Hawaii and western Alaska….
Study finds human-driven changes in climate and land-use in Amazon’s 3rd “1-in-100 year” drought since 2005
man-made warming is accelerating the movement of water through the ecosystem, which can cause drought even if precipitation does not decrease. Warming also causes changes in the large-scale patterns of air motion (atmospheric circulation) that reduces rainfall in this region
…the Amazon region does encounter periodic droughts. There was one in 2005, another in 2010, both of which were 100-year events, and the most recent one in 2015-2016.
[The authors] quantified the precipitation deficits and water storage on the ground. They also used two different vegetation measures of drought. The results showed that the most recent drought was unprecedented in severity. ……
…the authors found that the relationship between water temperatures and drought worked well for prior droughts (the 2005 and 2010 droughts as well as 1983 and 1998 droughts, also El Niño years) but fell apart in 2015-2016.
…the predicted 2015-2016 drought should not have been nearly as severe or as large as it was. The paper also reports that the 2015-2016 drought clearly exceeded that of the 100-year events in 2005 and 2010. So, in approximately one decade, this zone has had three 100-year events. Quite astonishing…
why was SST unable to explain the 2015-2016 drought, like it had for past events? Part of it has to do with land-use changes. That is, human changes to the land surface such as deforestation. Another part is related to warming from greenhouse gases…land-use changes can affect drought. As farmers deforest, for instance, they convert woodlands and forests into agricultural land. This changes not only the darkness (reflectivity) of the land, but it also impacts the transfer of water to and from the atmosphere (evapotranspiration).
how [does] warming affects droughts… As air temperatures increase, air is able to evaporate water more rapidly and dry out surfaces. At the same time, air can contain more water vapor so that when rain does occur, it is more often in heavy downpours. These two changes underlie what is referred to as an accelerated hydrological cycle. Simply put, man-made warming is accelerating the movement of water through the ecosystem, which can cause drought even if precipitation does not decrease. Warming also causes changes in the large-scale patterns of air motion (atmospheric circulation) that reduces rainfall in this region.
Dr. Wang, who told me:
Since oceanic forcing could not fully explain the severity of the latest drought, one will have to account for the roles of greenhouse gas warming, land use land cover changes, and/or dynamic ecosystem feedback in order to advance the understanding, attribution and prediction of extreme droughts in this region. The frequent recurrence of severe droughts in the recent decade may be a precursor of what the future might have in store for this regional climate and ecosystem.
…droughts in this part of the world create an increased risk for desertification and fire occurrence and hurt the region’s ecosystem, harm trees, and accelerate the release of carbon dioxide…
With each passing year, the odds get worse that climate change mitigation efforts will be able to stave off catastrophic warming of more than 2 degrees Celsius, or 3.6 degrees Fahrenheit.
A new study published on July 31 in Nature Climate Change is the opposite of reassuring when it comes to this math. Using statistical tools, the authors found that there’s a 5% chance Earth will warm 2 degrees or less by the end of this century and a 90% chance that temperatures will increase from 2.0 to 4.9°C if historical trends continue unabated. The other 5%, well that’s worst-case scenario runaway global warming—the kind of thing that keeps geoengineers up at night.
As for the ambitious 1.5°C target included in the Paris Agreement, there’s apparently only a 1% chance of meeting that (not so surprising considering the planet has already warmed 1°C since pre-industrial times). So as climate change deniers like President Trump, EPA chief Scott Pruitt, and many GOP lawmakers put their money on taking little to no action and somehow escaping devastating warming, in truth it will take a herculean global effort to avoid costly and harmful impacts.
The reality of human-caused climate change is increasingly clear for anyone to see. Last year was the hottest year on record, and the 12 warmed years on record have all occurred since 1998. 2017 is on track to be the second-warmest year on record; and this even in the absence of an El Niño warming event like 2016’s. According to NASA, the first six months of this year were 0.94°C above the 1950–1980 average…
…Adrian Raftery, a UW professor of statistics and sociology and lead author on the new study, said while their analysis is compatible with previous estimates, it shows “we’re closer to the margin than we think….The goal of 2 degrees is very much a best-case scenario,” said Raftery in a statement. “It is achievable, but only with major, sustained effort on all fronts over the next 80 years.”
…Richard Startz, an economist at the University of California at Santa Barbara who worked on the study, told Project Earth the most surprising finding was that population growth will not be a major factor in increased CO2 emissions over the course of the century. This is in large part because most of that growth will occur in Africa, where per capita emissions will remain relatively low.
What matters a lot more for future warming is actually carbon intensity. According to the study, even though carbon intensity has dropped in recent decades as countries increase energy efficiency and enact carbon-reducing policies, it will need to drop much more to see the kind of progress the global climate community is aiming for with the Paris Agreement targets.
“Our study already assumes that the trends in carbon intensity will continue to improve,” said Startz. “So more reductions in carbon intensity aren’t enough. We need much faster reductions in carbon intensity than we’ve already been seeing.”
Startz said in his opinion there are two primary ways to accomplish this: Financial incentives to reduce carbon emissions—like carbon taxes or cap-and-trade programs—and a lot more support for scientific research that would help reduce emissions. “For example, the invention of practical LED lighting has been a small but significant achievement in reducing energy needs,” he said. “If someone could greatly increase battery cost-effectiveness, that would buy us a lot.”