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April 8th, 2017:

Fasten your seat belts: Climate change could add to turbulence during air travel

Flight turbulence could increase significantly under climate change, a study warns, potentially upping the risk of injury — or at least flight anxiety — for future airline passengers. Furthermore, fuel and maintenance costs for carriers could rise.

An increase in atmospheric carbon dioxide concentrations could cause changes in the jet stream over the North Atlantic flight corridor, leading to a spike in air turbulence, suggests the research conducted by atmospheric scientist Paul Williams of the University of Reading.

By the middle of the century, with no effort to reduce atmospheric concentrations of carbon dioxide, the volume of airspace experiencing light turbulence would increase by about 59 percent.

Airspace experiencing severe turbulence could increase by anywhere from 36 percent to 188 percent, the study found.

“We’re particularly interested in severe turbulence, because that’s the kind of turbulence that’s strong enough to hospitalize people,” Williams told The Washington Post.

Forecasting algorithms can help pilots anticipate and avoid turbulent patches. But the research does suggest that future fliers could be in for a bumpier ride.

The paper builds on a 2013 study in the journal Nature Climate Change by Williams and colleague Manoj Joshi of the University of East Anglia, which found an increase in moderate-to-severe turbulence in the North Atlantic as a result of climate change.

The study did not investigate the effects on lighter or more severe degrees of turbulence. In the new paper, Williams expanded the study to light turbulence, and more severe conditions.

Light turbulence typically comes with only minor discomfort for passengers, perhaps an increase in nausea or anxiety. Severe turbulence has been known to cause injuries and even hospitalizations.

Williams focused on an area in the North Atlantic known for heavy air traffic, particularly between Europe and North America, and limited his simulations to winter, when turbulence is known to be at its highest.

He examined 21 different wind-related characteristics known to be indicators of air turbulence levels, including wind speed and changes in air flow direction.

The study found an increase in turbulence across the spectrum. Light turbulence was projected to increase by an average of 59 percent, light-to-moderate by 75 percent, moderate by 94 percent, moderate-to-severe by 127 percent and severe by 149 percent, although there’s substantial uncertainty associated with the more severe categories.

Williams stressed that severe turbulence would remain rare — even with the increase. But even an increase in light turbulence can cause greater wear and tear on planes or force pilots to use extra fuel redirecting their flight paths to avoid rough patches.

The increase in air turbulence may apply only to the North Atlantic, researchers not involved in the study said.

“Regional variations of this increase may be quite uncertain, particularly in the higher latitudes where other aspects of circulation change that are less well understood and more model-dependent may dominate,” said Isla Simpson, a scientist at the National Center for Atmospheric Research, in an emailed comment to The Post.

Kristopher Karnauskas, an atmospheric and oceanic sciences expert at the University of Colorado at Boulder, said the behavior of the jet stream over the Pacific may respond differently to climate change.

The study builds on an area of climate science that increasingly suggests rising global temperatures can cause changes in atmospheric airflow, including shifts in major air currents known as jet streams.

Because the equator is the warmest part of the planet, and warm air takes up more space than cold air, the atmosphere tends to be thicker around the center of Earth than at the poles. As a result, there’s a kind of downhill atmospheric slope from the equator to the poles over which air flows. While this is happening, Earth is constantly spinning, pushing airflow eastward. In the North Atlantic, the result is a jet stream — a meandering, wavy current flowing around the planet from west to east.

As the planet grows hotter, however, warming air near the surface could bring about changes in the atmospheric slope between equator and poles. Models such as the one used in Williams’ new paper have suggested that the jet stream could become stronger as a result, bringing about an increase in the types of wind patterns that lead to increased air turbulence.

Some research has already begun to detect changes in large-scale atmospheric currents. Other scientists have suggested that rapid warming in the Arctic is actually causing the jet stream to weaken.

There remains considerable uncertainty about how airflow near Earth’s surface might change in the future, Simpson said. But she said scientists are becoming more confident about the changes “that we expect to happen higher up, near the altitude where planes fly.”

Examining these issues can lead to a better understanding of the effects of climate change on aviation, Karnauskas said.

“I think it’s been decades that all of the attention has been on the impact of such industries like aviation on climate, but this is something that’s flipping it around and looking at the impact of climate on aviation,” he said. “If we can really understand the two-way street that we’re dealing with, that’s really going to help us understand ultimately how the climate will change in the future as a coupled system between the people and the atmosphere.”

Combined effect of brighter sun and CO₂ emissions could lead to unprecedented warming

The same carbon concentrations will cause more warming in future than in previous periods of high carbon dioxide due to the sun becoming stronger, experts warn

Carbon dioxide concentrations are heading towards values not seen in the past 200 million years. The sun has also been gradually getting stronger over time. Put together, these facts mean the climate may be heading towards warmth not seen in the past half a billion years.

A lot has happened on Earth since 500,000,000BC. Continents, oceans and mountain ranges have come and gone, and complex life has evolved and moved from the oceans onto the land and into the air. Most of these changes occur on very long timescales of millions of years or more. However, over the past 150 years global temperatures have increased by about 1°C, ice caps and glaciers have retreated, polar sea ice has melted, and sea levels have risen.

Some will point out that Earth’s climate has undergone similar changes before. So what’s the big deal this time?

Scientists can seek to understand past climates by looking at the evidence locked away in rocks, sediments and fossils. What this tells us is that yes, the climate has changed in the past, but the current speed of change is highly unusual. For instance, carbon dioxide hasn’t been added to the atmosphere as rapidly as today for at least the past 66m years.

In fact, if we continue on our current path and exploit all convention fossil fuels, then as well as the rate of CO₂ emissions, the absolute climate warming is also likely to be unprecedented in at least the past 420m years. That’s according to a new study we have published in Nature Communications.

In terms of geological time, 1°C of global warming isn’t particularly unusual. For much of its history the planet was significantly warmer than today, and in fact more often than not Earth was in what is termed a “greenhouse” climate state. During the last greenhouse state 50m years ago, global average temperatures were 10-15°C warmer than today, the polar regions were ice-free, palm trees grew on the coast of Antarctica, and alligators and turtles wallowed in swamp-forests in what is now the frozen Canadian Arctic.

In contrast, despite our current warming, we are still technically in an “icehouse” climate state, which simply means there is ice on both poles. The Earth has naturally cycled between these two climate states every 300m years or so.

Just prior to the industrial revolution, for every million molecules in the atmosphere, about 280 of them were CO₂ molecules (280 parts per million, or ppm). Today, due primarily to the burning of fossil fuels, concentrations are about 400 ppm. In the absence of any efforts to curtail our emissions, burning of conventional fossil fuels will cause CO₂ concentrations to be around 2,000ppm by the year 2250.

This is of course a lot of CO₂, but the geological record tells us that the Earth has experienced similar concentrations several times in the past. For instance, our new compilation of data shows that during the Triassic, around 200m years ago, when dinosaurs first evolved, Earth had a greenhouse climate state with atmospheric CO₂ around 2,000-3,000ppm.

High concentrations of carbon dioxide don’t necessarily make the world totally uninhabitable: the dinosaurs thrived, after all.

But that doesn’t mean this is no big deal. For a start, there is no doubt that humanity will face major socio-economic challenges dealing with the dramatic and rapid climate change that will result from the rapid rise to 2,000 or more ppm.

But our new study also shows that the same carbon concentrations will cause more warming in future than in previous periods of high carbon dioxide. This is because the Earth’s temperature does not just depend on the level of CO₂ (or other greenhouse gases) in the atmosphere. All our energy ultimately comes from the sun, and due to the way the sun generates energy through nuclear fusion of hydrogen into helium, its brightness has increased over time. Four and a half billion years ago when the Earth was young the sun was around 30 per cent less bright.

What really matters is the combined effect of the sun’s changing strength and the varying greenhouse effect. Looking through geological history we generally found that as the sun became stronger through time, atmospheric CO₂ gradually decreased. On average, both changes cancelled each other out.

But what about in the future? We found no past time period when the drivers of climate, or climate forcing, was as high as it will be in the future if we burn all the readily available fossil fuel. Nothing like it has been recorded in the rock record for at least 420m years.

A central pillar of geological science is the uniformitarian principle: that “the present is the key to the past”. If we carry on burning fossil fuels as we are at present, by 2250 this old adage is sadly no longer likely to be true. It is doubtful that this high-CO₂ future will have a counterpart, even in the vastness of the geological record.

Gavin Foster is a professor of isotope geochemistry at the University of Southampton, Dana Royer is a professor of earth and environmental sciences at Wesleyan University and Dan Lunt is a professor of climate science at the University of Bristol. This article first appeared on The Conversation (