Communities are already experiencing a changing climate as temperature extremes become a familiar trend around the globe. How much is temperature to blame when hospital visits increase during heat waves and cold spells? What role do adaptations like indoor heating and cooling systems play in blunting these effects? And, at what cost? Empirical evidence of the risks extreme temperatures pose to human health is limited since fatalities often come from periods of heat or cold that worsen underlying conditions. Individual deaths are rarely attributed to temperature surges, so public health officials and policymakers often invest less in addressing and responding to climate change. The answers to these questions would inform policymakers, city planners, business leaders, and a range of stakeholders who are preparing to mitigate and adapt as the climate becomes more unstable. Read More
]]>by Todd Bates, Rutgers University
New research by Rutgers scientists reaffirms that modern sea-level rise is linked to human activities and not to changes in Earth’s orbit.
Surprisingly, the Earth had nearly ice-free conditions with carbon dioxide levels not much higher than today and had glacial periods in times previously believed to be ice-free over the last 66 million years, according to a paper published in the journal Science Advances.
“Our team showed that the Earth’s history of glaciation was more complex than previously thought,” said lead author Kenneth G. Miller, a Distinguished Professor in the Department of Earth and Planetary Sciences in the School of Arts and Sciences at Rutgers University-New Brunswick. “Although carbon dioxide levels had an important influence on ice-free periods, minor variations in the Earth’s orbit were the dominant factor in terms of ice volume and sea-level changes – until modern times.”
Sea-level rise, which has accelerated in recent decades, threatens to permanently inundate densely populated coastal cities and communities, other low-lying lands and costly infrastructure by 2100. It also poses a grave threat to many ecosystems and economies.
The paper reconstructed the history of sea levels and glaciation since the age of the dinosaurs ended. Scientists compared estimates of the global average sea level, based on deep-sea geochemistry data, with continental margin records. Continental margins, which include the relatively shallow ocean waters over a continental shelf, can extend hundreds of miles from the coast.
The study showed that periods of nearly ice-free conditions, such as 17 million to 13 million years ago, occurred when the concentration of atmospheric carbon dioxide – a key greenhouse gas driving climate change – was not much higher than today. However, glacial periods occurred when the Earth was previously thought to be ice-free, such as from 48 million to 34 million years ago.
“We demonstrate that although atmospheric carbon dioxide had an important influence on ice-free periods on Earth, ice volume and sea-level changes prior to human influences were linked primarily to minor variations in the Earth’s orbit and distance from the sun,” Miller said.
The largest sea-level decline took place during the last glacial period about 20,000 years ago, when the water level dropped by about 400 feet. That was followed by a foot per decade rise in sea level – a rapid pace that slowed from 10,000 to 2,000 years ago. Sea-level rise was then at a standstill until around 1900, when rates began rising as human activities began influencing the climate.
Future work reconstructing the history of sea-level changes before 48 million years ago is needed to determine the times when the Earth was entirely ice-free, the role of atmospheric carbon dioxide in glaciation and the cause of the natural fall in atmospheric carbon dioxide before humans.
]]>by Todd Bates, Rutgers University
Heat stress from extreme heat and humidity will annually affect areas now home to 1.2 billion people by 2100, assuming current greenhouse gas emissions, according to a Rutgers study.
That’s more than four times the number of people affected today, and more than 12 times the number who would have been affected without industrial era global warming.
The research is published in the journal Environmental Research Letters.
Rising global temperatures are increasing exposure to heat stress, which harms human health, agriculture, the economy and the environment. Most climate studies on projected heat stress have focused on heat extremes but not considered the role of humidity, another key driver.
“When we look at the risks of a warmer planet, we need to pay particular attention to combined extremes of heat and humidity, which are especially dangerous to human health,” said senior author Robert E. Kopp, director of the Rutgers Institute of Earth, Ocean, and Atmospheric Sciences and a professor in the Department of Earth and Planetary Sciences in the School of Arts and Sciences at Rutgers University-New Brunswick.
“Every bit of global warming makes hot, humid days more frequent and intense. In New York City, for example, the hottest, most humid day in a typical year already occurs about 11 times more frequently than it would have in the 19th century,” said lead author Dawei Li, a former Rutgers post-doctoral associate now at the University of Massachusetts.
Heat stress is caused by the body’s inability to cool down properly through sweating. Body temperature can rise rapidly, and high temperatures may damage the brain and other vital organs. Heat stress ranges from milder conditions like heat rash and heat cramps to heat exhaustion, the most common type. Heat stroke, the most serious heat-related illness, can kill or cause permanent disability without emergency treatment, according to the U.S. Centers for Disease Control and Prevention.
The study looked at how combined extremes of heat and humidity increase on a warming Earth, using 40 climate simulations to get statistics on rare events. The study focused on a measure of heat stress that accounts for temperature, humidity and other environmental factors, including wind speed, sun angle and solar and infrared radiation.
Annual exposure to extreme heat and humidity in excess of safety guidelines is projected to affect areas currently home to about 500 million people if the planet warms by 1.5 degrees Celsius (2.7 degrees Fahrenheit) and nearly 800 million at 2 degrees Celsius (3.6 degrees Fahrenheit). The planet has already warmed by about 1.2 degrees (2.2 degrees Fahrenheit) above late 19th century levels.
An estimated 1.2 billion people would be affected with 3 degrees Celsius (5.4 degrees Fahrenheit) of warming, as expected by the end of this century under current global policies.
In New York City, extreme heat and humidity, comparable to the worst day in a typical year today, is projected to occur on four days in a typical year with global warming of 1.5 degrees Celsius (2.7 degrees Fahrenheit) and about eight days per year with warming of 2 degrees Celsius (3.6 degrees Fahrenheit). With 3 degrees Celsius (5.4 degrees Fahrenheit) of warming, extreme heat and humidity are projected to occur for about 24 days in a typical year.
The paper was co-authored by Jiacan Yuan, a former Rutgers assistant research professor in the Department of Earth and Planetary Sciences who is now at Fudan University in China.
]]>by Keely Swan, Princeton University
Scientists agree that sea levels will continue to rise this century, but projections beyond 2050 are much more uncertain regarding exactly how much higher ocean levels will be by 2100. While actions to protect against 2050 sea-level rise have a secure scientific basis, this range in late-century estimates makes it difficult for coastal communities to plan their long-term adaptation strategies.
Princeton University researchers at the Center for Policy Research on Energy and the Environment have developed a new framework allowing urban planners and policymakers to consider a combination of responses to sea-level rise (e.g., levees, storm surge barriers, elevating buildings, retreat) and, if hard structures, how high these protections should be built, depending on their tolerance for risk and the projected financial losses to a particular area due to flooding. The paper was published in Earth’s Future.
Over the past 100 years, relative sea level measured at The Battery, the historic park at the southernmost tip of Manhattan Island, New York, has increased by 0.285 meters or just under 1 foot, according to the National Oceanic and Atmospheric Administration. Because of global warming, scientists expect this rate of sea-level rise to accelerate in the coming decades. However, there is uncertainty regarding how much greenhouse gas emissions will change and how much of Antarctica will melt in response to a warming climate.
Scientific perspectives on these issues result in different projections of global average sea-level rise. For example, local sea levels at the Battery are expected to rise between 0.6 m and 1.8 m from the beginning of this century to 2100. “We will be contending with more frequent, extreme flooding from coastal storms and high tides. These ‘100-year floods’ will become much more frequent – in some places, as often as once per year,” added co-author and leading climate scientist, Michael Oppenheimer.
Existing frameworks for calculating how high to elevate structures to avoid future floods only consider extreme water levels, not the damages that flooding can cause. This may lead to under- or over-estimates in terms of how high to raise a structure.
The authors introduce a new “flood damage allowance” approach that connects extreme water levels with projected damages, incorporating both uncertainty regarding sea-level rise, as well as people’s individual tolerance of risk.
“Our approach allows decision-makers to specify their own acceptable level of risk, a protection strategy type – such as elevation, storm surge barrier, or coastal retreat – and their assumptions about how much the Antarctic Ice Sheet will melt,” said D.J. Rasmussen, lead author and a Ph.D. candidate at the Woodrow Wilson School of Public and International Affairs at Princeton. “Our framework could help inform the Army Corps of Engineers’ efforts to design climate change adaptation projects.”
The authors use Manhattan as an example to illustrate their framework. New York City has experienced tremendous losses due to flooding, as it is among the top global cities exposed to coastal flood threats; just in Manhattan, there are over $50 billion of assets are currently within the 100-year flood plain. Some of the key responses the flood damage allowances approach explores are:
While planners will still need to do more detailed assessments of the feasibility of various sea defense models in a particular location, this simpler model can identify promising strategies before planners invest in further, more complex engineering and financial models. Because of the study’s modeling simplifications, the authors do not propose specific recommendations for how NYC should respond; rather, the framework illustrates that under different circumstances, some approaches may have certain advantages over others.
For example, in the wake of Hurricane Sandy, the Army Corps of Engineers is currently exploring the use of storm surge barriers to protect New York City from future sea-level rise and more frequent coastal floods. A key question is, “How high to build the barriers?” The answer depends on input from the engineers and expert judgments about how much and how quickly Antarctica will melt. The authors’ framework can facilitate estimates of how high to build the storm surge barriers and allow planners to explore the impact of different factors on recommended surge barrier heights.
“As coastal cities and communities prepare for a changing coastline and climate in the coming decades, tools like this one that incorporate uncertainty and integrate oceanographic and financial information will help planners develop a more thorough analysis of their best defense options,” the researchers said; “In the end, a variety of strategies will be needed to protect most coastal cities.”
]]>by Sarah Stanley, EOS
Millions of people around the world live in coastal communities that are directly threatened by sea level rise. In a new review, Kopp et al. explore the state of sea level science and highlight key challenges in using it to inform adaptation responses to evolving coastlines. Read More
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