Nav: Home

Controlling future summer weather extremes still within our grasp

October 31, 2018

Continued burning of fossil fuels is likely to fuel even more extreme summers than that of 2018 because of its impact on the jet stream. The rapid disappearance of aerosols produced by pollution may, however, mitigate the impact until mid-century if countries like China phase out these fuels, according to an international team of climate scientists using climate models to predict changes in the occurrence of so-called Quasi-Resonant Amplification (QRA) events associated with persistent weather extremes.

These extreme paths for the jet stream bring about flooding, drought and wildfires. In 2018, summer weather included flooding in Japan, record heat waves in North America, Europe and Asia, wildfires in Greece and even parts of the Arctic. Heat and drought in California led to the worst wildfire season ever recorded.

The jet stream and extreme weather events

QRA events produce extreme summer weather when the jet stream exhibits broad north-south meanders and becomes stationary with the peaks and troughs locked in place.

"Most stationary jet stream disturbances will dissipate over time," said Michael Mann, distinguished professor of atmospheric science and director, Earth System Science Center. "However, under certain circumstances the wave disturbance is effectively constrained by an atmospheric wave guide, something similar to the way a coaxial cable guides a television signal. Disturbances then cannot easily dissipate and very large amplitude swings in the jet stream north and south can remain in place as it rounds the globe."

"If the same weather persists for weeks on end in one region, then sunny days can turn into a serious heat wave and drought, and lasting rains can lead to flooding," said Stefan Rahmstorf, Potsdam Institute for Climate Impact Research (PIK), Germany.

In summer 2018, climate change impacts on extreme weather were no longer subtle, according to Mann.

"It played out in real time on our television screens and newspaper headlines in the form of an unprecedented hemisphere-wide pattern of extreme floods, droughts, heat waves and wildfires," Mann added.

Quasi-Resonant Amplification's role

Mann notes that the phenomenon of QRA played an important role in producing that hemispheric array of unprecedented weather events.

Previous work by Mann and colleagues showed a connection between extreme climate events and climate-induced changes in the jet stream. While researchers cannot accurately identify QRA events in climate models, one thing the climate models capture very well is temperature change.

"QRA events have been shown to have a well-defined signature in terms of the latitudinal variation in temperature in the lower atmosphere," explained Mann. "The change in temperature with latitude and how it responds to increasing greenhouse gas concentrations depends on physics that are well understood and well represented by the climate models."

The researchers found that the pattern of amplified Arctic warming -- Arctic Amplification -- that slows down the jet stream also increases the frequency of QRA episodes.

Study co-author Dim Coumou, who is both at PIK and VU Amsterdam said we do not trust climate models enough yet to predict these types of extreme weather episodes because the models are too coarse.

"However, the models do faithfully produce large scale patterns of temperature change," added co-author Kai Kornhuber of PIK.

The researchers report today (Oct. 31.) in Science Advances that the amplified Arctic warming, called Arctic Amplification, associated with human-caused climate change both slows down the jet stream and increases the frequency of QRA episodes.

They found that climate models, when used to project future changes in extreme weather behavior -- because they are unable to capture the phenomenon of QRA -- are likely underestimating how future climate change could lead to more persistent summer weather extremes like those during summer 2018. If carbon dioxide continues to be added to the atmosphere, the incidence of QRA and associated extreme weather events would continue to increase at the same rate they have over the past decades.

Aerosol's effect on regulating temperatures

However, greenhouse gases are not the only consideration when looking at the future of the Earth's climate. Although the U.S. and Europe have switched to "cleaner" coal-burning methods, which remove aerosol-generating pollutants from emissions, many other areas of the world have not. Aerosols are particles suspended in the air.

If these countries, through midcentury, switch to cleaner coal-burning technology, then the mid-latitude areas of the world will warm and Arctic Amplification will diminish. This will occur because aerosols, especially in the mid-latitudes where there is abundant sun, cool the Earth by reflecting heat away from the planet. Without those aerosols, that area of the Earth will warm, mitigating any further increase in QRAs as the difference in warming between the Arctic and mid latitudes diminishes.

However, by mid-century, once the aerosols are no longer produced, greenhouse warming once more dominates climate. Curtailing the burning of fossil fuels can prevent an increase in persistent summer weather extremes, though the current rate of occurrence of summers like 2018 will likely persist. "The future is still very much in our hands when it comes to dangerous and damaging summer weather extremes." Said Mann. "It's simply a matter of our willpower to transition quickly from fossil fuels to renewable energy."
Also working on this project are Sonya K. Miller, programmer analyst, Penn State; Byron A. Steinman, assistant professor of earth and environmental sciences and at Large Lakes Observatory, University of Minnesota: Duluth; and Kai Kornhuber and Stefan Petri, Earth System Analysis, Potsdam Institute for Climate Impact Research.

The Federal Ministry of Education and Research, Germany, partially funded this project.

Penn State

Related Climate Models Articles:

Individual climate models may not provide the complete picture
Equilibrium climate sensitivity -- how sensitive the Earth's climate is to changes in atmospheric carbon dioxide -- may be underestimated in individual climate models, according to a team of climate scientists.
Deep neural networks speed up weather and climate models
A team of environmental and computation scientists at the US Department of Energy's (DOE) Argonne National Laboratory are collaborating to use deep neural networks, a type of machine learning, to replace the parameterizations of certain physical schemes in the Weather Research and Forecasting Model, an extremely comprehensive model that simulates the evolution of many aspects of the physical world around us.
Climate models and geology reveal new insights into the East Asian monsoon
A team of scientists, led by the University of Bristol, have used climate models and geological records to better understand changes in the East Asian monsoon over long geologic time scales.
Multifactor models reveal worse picture of climate change impact on marine life
Rising ocean temperatures have long been linked to negative impacts for marine life, but a Florida State University team has found that the long-term outlook for many marine species is much more complex -- and possibly bleaker -- than scientists previously believed.
Airborne lidar system poised to improve accuracy of climate change models
Researchers have developed a laser-based system that can be used for airborne measurement of important atmospheric gases with unprecedented accuracy and resolution.
Pulses of sinking carbon reaching the deep sea are not captured in global climate models
A new study by MBARI scientists shows that pulses of sinking debris carry large amounts of carbon to the deep seafloor, but are poorly represented in global climate models.
Study brings new climate models of small star TRAPPIST 1's seven intriguing worlds
New research from a University of Washington-led team of astronomers gives updated climate models for the seven planets around the star TRAPPIST-1.
Current climate models underestimate warming by black carbon aerosol
Researchers in the School of Engineering & Applied Science have discovered a new, natural law that sheds light on the fundamental relationship between coated black carbon and light absorption.
Improving climate models to account for plant behavior yields 'goodish' news
Climate scientists have not been properly accounting for what plants do at night, and that, it turns out, is a mistake.
Climate models fail to simulate recent air-pressure changes over Greenland
Climatologists may be unable to accurately predict regional climate change over the North Atlantic because computer simulations have failed to include real data from the Greenland region over the last three decades -- and it could lead to regional climate predictions for the UK and parts of Europe being inaccurate.
More Climate Models News and Climate Models Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#543 Give a Nerd a Gift
Yup, you guessed it... it's Science for the People's annual holiday episode that helps you figure out what sciency books and gifts to get that special nerd on your list. Or maybe you're looking to build up your reading list for the holiday break and a geeky Christmas sweater to wear to an upcoming party. Returning are pop-science power-readers John Dupuis and Joanne Manaster to dish on the best science books they read this past year. And Rachelle Saunders and Bethany Brookshire squee in delight over some truly delightful science-themed non-book objects for those whose bookshelves are already full. Since...
Now Playing: Radiolab

An Announcement from Radiolab