Get used to heat waves: Extreme El Nino events to double

Extreme weather events fueled by unusually strong El Ninos, such as the 1983 heatwave that led to the Ash Wednesday bushfires in Australia, are likely to double in number as our planet warms.

An international team of scientists from organizations including the ARC Centre of Excellence for Climate System Science (CoECSS), the US National Oceanic and Atmospheric Administration and CSIRO, published their findings in the journal Nature Climate Change.

"We currently experience an unusually strong El Ni?o event every 20 years. Our research shows this will double to one event every 10 years," said co-author, Dr Agus Santoso of CoECSS.

"El Nino events are a multi-dimensional problem, and only now are we starting to understand better how they respond to global warming," said Dr Santoso. Extreme El Ni?o events develop differently from standard El Ninos, which first appear in the western Pacific. Extreme El Nino's occur when sea surface temperatures exceeding 28?C develop in the normally cold and dry eastern equatorial Pacific Ocean. This different location for the origin of the temperature

increase causes massive changes in global rainfall patterns.

"The question of how global warming will change the frequency of extreme El Ni?o events has challenged scientists for more than 20 years," said co-author Dr Mike McPhaden of US National Oceanic and Atmospheric Administration.

"This research is the first comprehensive examination of the issue to produce robust and convincing results," said Dr McPhaden.

The impacts of extreme El Ni?o events extend to every continent across the globe.

The 1997-98 event alone caused $35-45 US billion in damage and claimed an estimated 23,000 human lives worldwide.

"During an extreme El Ni?o event countries in the western Pacific, such as Australia and Indonesia, experienced devastating droughts and wild fires, while catastrophic floods occurred in the eastern equatorial region of Ecuador and northern Peru," said lead author, CSIRO's Dr Wenju Cai

In Australia, the drought and dry conditions induced by the 1982-83 extreme El Ni?o preconditioned the Ash Wednesday Bushfire in southeast Australia, leading to 75 fatalities.

To achieve their results, the team examined 20 climate models that consistently simulate major rainfall reorganization during extreme El Ni?o events. They found a substantial increase in events from the present-day through the next 100 years as the eastern Pacific Ocean warmed in response to global warming.

"This latest research based on rainfall patterns, suggests that extreme El Ni?o events are likely to double in frequency as the world warms leading to direct impacts on extreme weather events worldwide."

"For Australia, this could mean summer heat waves, like that recently experienced in the south-east of the country, could get an additional boost if they coincide with extreme El Ninos," said co-author, Professor Matthew England from CoECSS.

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A warming world will further intensify extreme precipitation events

April 4, 2013

Heavy precipitation.

According to a newly-published NOAA-led study in Geophysical Research Letters, as the globe warms from rising atmospheric concentrations of greenhouse gases, more moisture in a warmer atmosphere will make the most extreme precipitation events more intense.

The study, conducted by a team of researchers from the North Carolina State University’s Cooperative Institute for Climate and Satellites-North Carolina (CICS-NC), NOAA’s National Climatic Data Center (NCDC), the Desert Research Institute, University of Wisconsin-Madison, and ERT, Inc., reports that the extra moisture due to a warmer atmosphere dominates all other factors and leads to notable increases in the most intense precipitation rates.

Percent maximum daily preciptation difference (2071-2100) - (1971-2000).

Download here (Credit: NOAA)

The study also shows a 20-30 percent expected increase in the maximum precipitation possible over large portions of the Northern Hemisphere by the end of the 21st century if greenhouse gases continue to rise at a high emissions rate.

“We have high confidence that the most extreme rainfalls will become even more intense, as it is virtually certain that the atmosphere will provide more water to fuel these events,” said Kenneth Kunkel, Ph.D., senior research professor at CICS-NC and lead author of the paper.

The paper looked at three factors that go into the maximum precipitation value possible in any given location: moisture in the atmosphere, upward motion of air in the atmosphere, and horizontal winds. The team examined climate model data to understand how a continued course of high greenhouse gas emissions would influence the potential maximum precipitation. While greenhouse gas increases did not substantially change the maximum upward motion of the atmosphere or horizontal winds, the models did show a 20-30 percent increase in maximum moisture in the atmosphere, which led to a corresponding increase in the maximum precipitation value.

Rainy day.

The findings of this report could inform “design values,” or precipitation amounts, used by water resource managers, insurance and building sectors in modeling the risk due to catastrophic precipitation amounts. Engineers use design values to determine the design of water impoundments and runoff control structures, such as dams, culverts, and detention ponds.

“Our next challenge is to translate this research into local and regional new design values that can be used for identifying risks and mitigating potential disasters. Findings of this study, and others like it, could lead to new information for engineers and developers that will save lives and major infrastructure investments,” said Thomas R. Karl, L.H.D., director of NOAA’s NCDC in Asheville, N.C., and co-author on the paper.

The study, Probable Maximum Precipitation (PMP) and Climate Change, can be viewed online.

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New analyses find evidence of human-caused climate change in half of the 12 extreme weather and climate events analyzed from 2012

September 5, 2013

The "Explaining Extreme Events of 2012 from a Climate Perspective" report was published today by the Bulletin of the American Meteorological Society. (Full report).

High resolution (Credit: U.S. Navy)

Human influences are having an impact on some extreme weather and climate events, according to the report “Explaining Extreme Events of 2012 from a Climate Perspective” released today by the Bulletin of the American Meteorological Society. Overall, 18 different research teams from around the world contributed to the peer-reviewed report that examined the causes of 12 extreme events that occurred on five continents and in the Arctic during 2012. Scientists from NOAA served as three of the four lead editors on the report.
The report shows that the effects of natural weather and climate fluctuations played a key role in the intensity and evolution of the 2012 extreme events. However, in some events, the analyses revealed compelling evidence that human-caused climate change, through the emission of heat-trapping gases, also contributed to the extreme event.

“This report adds to a growing ability of climate science to untangle the complexities of understanding natural and human-induced factors contributing to specific extreme weather and climate events,” said Thomas R. Karl, L.H.D, director of NOAA’s National Climatic Data Center (NCDC). “Nonetheless, determining the causes of extreme events remains challenging.”

In addition to investigating the causes of these extreme events, the multiple analyses of four of the events — the warm temperatures in the United States, the record-low levels of Arctic sea ice, and the heavy rain in both northern Europe and eastern Australia — allowed the scientists to compare and contrast the strengths and weaknesses of their various methods of analysis. Despite their different strategies, there was considerable agreement between the assessments of the same events.

Thomas Peterson, Ph.D., principal scientist at NOAA’s NCDC and one of the lead editors on the report, said, “Scientists around the world assessed a wide variety of potential contributing factors to these major extreme events that, in many cases, had large impacts on society. Understanding the range of influences on extreme events helps us to better understand how and why extremes are changing."

Key findings include:

Location and type of events analyzed in the Paper.

High resolution (Credit: NOAA)

Heat Wave and Drought in United States:

Human-induced climate change had little impact on the lack of precipitation in the central United States in 2012.The 2012 spring and summer heat waves in the U.S. can be mainly explained by natural atmospheric dynamics, however, human-induced climate change was found to be a factor in the magnitude of warmth and was found to have affected the likelihood of such heat waves.  For example: High temperatures, such as those experienced in the U.S. in 2012 are now likely to occur four times as frequently due to human-induced climate change.Approximately 35 percent of the extreme warmth experienced in the eastern U.S. between March and May 2012 can be attributed to human-induced climate change.  

Hurricane Sandy Inundation Probability:

The record-setting impacts of Sandy were largely attributable to the massive storm surge and resulting inundation from the onshore-directed storm path coincident with high tide. However, climate-change related increases in sea level have nearly doubled today’s annual probability of a Sandy-level flood recurrence as compared to 1950. Ongoing natural and human-induced forcing of sea level ensures that Sandy-level inundation events will occur more frequently in the future from storms with less intensity and lower storm surge than Sandy. 

Arctic Sea Ice:

The extremely low Arctic sea ice extent in summer 2012 resulted primarily from the melting of younger, thin ice from a warmed atmosphere and ocean. This event cannot be explained by natural variability alone. Summer Arctic sea ice extent will continue to decrease in the future, and is expected to be largely absent by mid-century.  

Global Rainfall Events:

The unusually high amount of summer rainfall in the United Kingdom in 2012 was largely the result of natural variability. However, there is evidence that rainfall totals are influenced by increases in sea surface temperature and atmospheric moisture which may be linked to human influences on climate.The magnitude of the extreme rainfall experienced over southeastern Australia between October 2011 and March 2012 was mainly associated with La Niña conditions. However, the likelihood of above-average precipitation during March was found to have increased by 5 percent to 15 percent because of human influences on the climate. Extreme rainfall events such as the December 2011 two-day rainfall in Golden Bay, New Zealand, are more likely to occur due to a 1 percent to 5 percent increase in available moisture resulting from increased levels of greenhouse gases in the atmosphere.The July 2012 extreme rainfall events in North China and southwestern Japan were mainly due to natural variability. 

The report was edited by Peterson, along with Martin P. Hoerling, NOAA’s Earth System Research Laboratory; Peter A. Stott, UK Met Office Hadley Centre and Stephanie C. Herring of NCDC and written by 78 scientists from 11 countries. View the full report online.

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Climate Change Panel Predicts More Intense Weather Events (ContributorNetwork)

According to NPR, a recent meeting of the United Nations Intergovernmental Panel on Climate Change, which included more than 200 scientists, concluded with a report stating it expects climate change to bring more intense weather events. The panel specifically noted more rainfall, heat waves and other natural disasters are in the forecast as a result of climate change.

The IPCC notes the frequency of heavy rainfall will likely increase this century in many different regions. Additionally, more powerful hurricanes and typhoons are likely to occur, but these events will see a gradual, small increase instead of a steep one. With the debut of this report, here are some facts about climate change:

* Since the industrial revolution, the burning of fuel and constant deforestation has led to the release of greenhouse gases, especially carbon dioxide, in the atmosphere, according to the Environmental Protection Agency.

* These greenhouse gases prevent heat from re-entering space and create a warming effect, also known as global warming or climate change, on the earth.

* The Washington State Department of Ecology notes while climate change can impact weather events, it also has the potential to impact agriculture, human health, water resources, and energy use.

* Despite the fact there is a warming trend, different regions will experience changes differently as well and there is the possibility that a few areas could see temperatures drop instead of increasing.

* In the late 1990s, numerous nations attempted to join together to establish the Kyoto Protocol, a treaty designed to ensure countries would commit to combating climate change.

* The U.S. failed to ratify the treaty over concerns that China and India would not have to follow the outlined changes or commit to reducing their own emissions.

* Nearly a decade later in Copenhagen, Denmark, world leaders met again to discuss and reach agreements on the growing concern of global warming.

* The 2009 summit focused on the dispute between the U.S. and China and if the nations couldn't agree it could have potentially killed any further international agreements at the summit.

* President Barack Obama also attended and spoke at the summit to help work out disagreements over China joining the pledge and although they fell short of expectations, agreements were finally reached.

Rachel Bogart provides an in-depth look at current environmental issues and local Chicago news stories. As a college student from the Chicago suburbs pursuing two science degrees, she applies her knowledge and passion to both topics to garner further public awareness.

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