Tag Archives: weather

Climate Change Equals Less Weather Predictability

NASA-Icemelt1

Severe weather often leads to human tragedy, and of course our crops, pets and property suffer too, as well as untold damage to numerous ecosystems. But whenever I see or read about a weather-induced catastrophe — local flooding or a super-typhoon halfway around the world — one thought always comes to mind: what kind of weather will my children face as long-term climate change takes hold.

Climate science offers continued predictions of doom and gloom: rising ocean levels, disappearing glaciers, stronger storms, longer droughts, more extreme weather.

But climate science also tells us that long-term climate change will make for generally less predictable weather. Our present day meteorologists armed with powerful computational climate models have become rather good at forecasting weather on local and global levels. Generally, we have a reasonably good idea of what our local weather will be tomorrow or next week or next month.

But a warming and changing climate adds much more uncertainty. William B. Gail, founder of the Global Weather Corporation and past president of the American Meteorological Society, cautions: there is a growing likelihood of increased unpredictability of our weather systems. Indeed, he predicts a new dark age, where climate change destroys our current understanding of weather patterns and undermines all our current, predictive weather models and forecasts. This is a huge problem for those of us who depend on accurate weather analytics for our livelihoods, especially farmers, fishing industries, aviation, ground transportation, and construction.

From NYT:

Imagine a future in which humanity’s accumulated wisdom about Earth — our vast experience with weather trends, fish spawning and migration patterns, plant pollination and much more — turns increasingly obsolete. As each decade passes, knowledge of Earth’s past becomes progressively less effective as a guide to the future. Civilization enters a dark age in its practical understanding of our planet.

To comprehend how this could occur, picture yourself in our grandchildren’s time, a century hence. Significant global warming has occurred, as scientists predicted. Nature’s longstanding, repeatable patterns — relied on for millenniums by humanity to plan everything from infrastructure to agriculture — are no longer so reliable. Cycles that have been largely unwavering during modern human history are disrupted by substantial changes in temperature and precipitation.

As Earth’s warming stabilizes, new patterns begin to appear. At first, they are confusing and hard to identify. Scientists note similarities to Earth’s emergence from the last ice age. These new patterns need many years — sometimes decades or more — to reveal themselves fully, even when monitored with our sophisticated observing systems. Until then, farmers will struggle to reliably predict new seasonal patterns and regularly plant the wrong crops. Early signs of major drought will go unrecognized, so costly irrigation will be built in the wrong places. Disruptive societal impacts will be widespread.

Such a dark age is a growing possibility. In a recent report, the National Academies of Sciences, Engineering and Medicine concluded that human-caused global warming was already altering patterns of some extreme weather events. But the report did not address the broader implication — that disrupting nature’s patterns could extend well beyond extreme weather, with far more pervasive impacts.

Our foundation of Earth knowledge, largely derived from historically observed patterns, has been central to society’s progress. Early cultures kept track of nature’s ebb and flow, passing improved knowledge about hunting and agriculture to each new generation. Science has accelerated this learning process through advanced observation methods and pattern discovery techniques. These allow us to anticipate the future with a consistency unimaginable to our ancestors.

But as Earth warms, our historical understanding will turn obsolete faster than we can replace it with new knowledge. Some patterns will change significantly; others will be largely unaffected, though it will be difficult to say what will change, by how much, and when.

The list of possible disruptions is long and alarming. We could see changes to the prevalence of crop and human pests, like locust plagues set off by drought conditions; forest fire frequency; the dynamics of the predator-prey food chain; the identification and productivity of reliably arable land, and the predictability of agriculture output.

Read the entire article here.

Image: Image pair of Muir Glacier and melt, Alaska. Left photo taken in 1882, by G.D. Hazard; Right photo taken in 2005 by Bruce F. Molnia. Courtesy: Glacier Photograph Collection, National Snow and Ice Data Center/World Data Center for Glaciology. NASA.

 

It’s Time for a Cat 6 Hurricane

Patricia_2015-10-23_1730Z

Amateur meteorologist that I am I wonder when my professional colleagues will extend the Saffir–Simpson hurricane wind scale (SSHWS). Currently the scale classifies hurricanes — western hemisphere tropical cyclones — on a scale of 1 to 5. Category 1 hurricanes encompass winds between 74-95 miles per hour; category 5 storms gyrate in excess of 157 miles per hour. As our global climate becomes increasingly warmer — which it is — our weather is becoming increasingly more volatile and extreme — longer hotter droughts, greater torrential rainfall, higher floods.

Category 5 will soon need to be supplemented. After all, the recent storm to hit the Pacific coast of Mexico — hurricane Patricia — reached sustained winds of 201 miles per hour; Typhoon Haiyan had a top wind spend of only 195 mph when it slammed the Phillippines in 2013 killing over 7,000 residents.

From the NYT:

Hurricane Patricia was a surprise. The eastern Pacific hurricane strengthened explosively before hitting the coast of Mexico, far exceeding projections of scientists who study such storms.

And while the storm’s strength dissipated quickly when it struck land, a question remained. What made it such a monster?

Explanations were all over the map, with theories that included climate change (or not), and El Niño.

But the answer is more complicated. The interplay of all the different kinds of warming going on in the Pacific at the moment can be difficult to sort out and, as with the recent hurricane, attributing a weather event to a single cause is unrealistic.

Gabriel Vecchi, head of the climate variations and predictability group at the geophysical fluid dynamics laboratory of the National Oceanic and Atmospheric Administration in Princeton, N.J., likened the challenge to the board game Clue.

“There’s all these suspects, and we have them all in the room right now,” he said. “The key is to go and systematically figure out who was where and when, so we can exclude people or phenomena.” Extending the metaphor, he noted that criminal suspects could work together as accomplices, and there could be a character not yet known. And, as in all mysteries, “You can have a twist ending.”

At the moment, the world’s largest ocean is a troublesome place, creating storms and causing problems for people and marine life across the Pacific Rim and beyond. A partial list includes the strong El Niño system that has formed along the Equator, and another unusually persistent zone of warm water that has been sitting off the North American coast, wryly called “the Blob.”

And a longer-term cycle of heating and cooling known as the Pacific Decadal Oscillation may be switching from a cooling phase to a warming phase. On top of all that is the grinding progress of climate change, caused by accumulation of greenhouse gases generated by human activity.

Each of these phenomena operates on a different time scale, but for now they appear to be synchronized, a little like the way the second hand, minute hand and hour hand line up at the stroke of midnight. And the collective effects could be very powerful.

Read the entire story here.

Image: Hurricane Patricia at peak intensity and approaching the Western Mexico on October 23, 2015. Courtesy: MODIS image, NASA’s Terra satellite. Public Domain.

Mid-21st Century Climate

Call it what you may, but regardless of labels most climate scientists agree that our future weather systems are much more likely to be more extreme: more prolonged and more violent.

From ars technica:

If there was one overarching point that the fifth Intergovernmental Panel on Climate Change report took pains to stress, it was that the degree of change in the global climate system since the mid-1950s is unusual in scope. Depending on what exactly you measure, the planet hasn’t seen conditions like these for decades to millennia. But that conclusion leaves us with a question: when exactly can we expect the climate to look radically new, with features that have no historical precedent?

The answer, according to a modeling study published in this week’s issue of Nature, is “very soon”—as soon as 2047 under a “business-as-usual” emission scenario and only 22 years later under a reduced emissions scenario. Tropical countries will likely be the first to enter this new age of climatic erraticness and could experience extreme temperatures monthly after 2050. This, the authors argue, underscores the need for robust efforts targeted not only at protecting those vulnerable countries but also the rich biodiversity that they harbor.

Developing an index, one model at a time

Before attempting to peer into the future, the authors, led by the University of Hawaii’s Camilo Mora, first had to ensure that they could accurately replicate the recent past. To do so, they pooled together the predictive capabilities of 39 different models, using near-surface air temperature as their indicator of choice.

For each model, they established the bounds of natural climate variability as the minimum and maximum values attained between 1860 and 2005. Simultaneously crunching the outputs from all of these models proved to be the right decision, as Mora and his colleagues consistently found that a multi-model average best fit the real data.

Next, they turned to two widely used emission scenarios, or Representative Concentration Pathways (RCP) as they’re known in modeling vernacular, to predict the arrival of different climates over a period extending from 2006 to 2100. The first scenario, RCP45, assumes a concerted mitigation initiative and anticipates CO2 concentrations of up to 538 ppm by 2100 (up from the current 393 ppm). The second, RCP85, is the trusty “business-as-usual” scenario that anticipates concentrations of up to 936 ppm by the same year.

Timing the new normals

While testing the sensitivity of their index, Mora and his colleagues concluded that the length of the reference period—the number of years between 1860 and 2005 used as a basis for establishing the limits of historical climate variability—had no effect on the ultimate outcome. A longer period would include more instances of temperature extremes, both low and high, so you would expect that it would yield a broader range of limits. That would mean that any projections of extreme future events might not seem so extreme by comparison.

In practice, it didn’t matter whether the authors used 20 years or 140 years as the length of their reference period. What did matter, they found, was the number of consecutive years where the climate was out of historical bounds. This makes intuitive sense: if you consider fewer consecutive years, the departure from “normal” will come sooner.

Rather than pick one arbitrary number of consecutive years versus another, the authors simply used all of the possible values from each of the 39 models. That accounts for the relatively large standard deviations in the estimated starting dates of exceptional climates—18 years for the RCP45 scenario and 14 years for the RCP85 scenario. That means that the first clear climate shift could occur as early as 2033 or as late as 2087.

Though temperature served as the main proxy for climate in their study, the authors also analyzed four other variables for the atmosphere and two for the ocean. These included evaporation, transpiration, sensible heat flux (the conductive transfer of heat from the planet’s surface to the atmosphere) and precipitation, as well as sea surface temperature and surface pH in the ocean.

Replacing temperature with, or considering it alongside, any of the other four variables for atmosphere did not change the timing of climate departures. This is because temperature is the most sensitive variable and therefore also the earliest to exceed the normal bounds of historical variability.

When examining the ocean through the prism of sea surface temperature, the researchers determined that it would reach its tipping point by 2051 or 2072 under the RCP85 and RCP45 scenarios, respectively. However, when they considered both sea surface temperature and surface pH together, the estimated tipping point was moved all the way up to this decade.

Seawater pH has an extremely narrow range of historical variability, and it moved out of this range 5 years ago, which caused the year of the climate departure to jump forward several decades. This may be an extreme case, but it serves as a stark reminder that the ocean is already on the edge of uncharted territory.

Read the entire article here.

Image courtesy of Salon.

Dark Lightning

It’s fascinating how a seemingly well-understood phenomenon, such as lightning, can still yield enormous surprises. Researchers have found that visible flashes of lightning can also be accompanied by non-visible, and more harmful, radiation such as x- and gamma-rays.

From the Washington Post:

A lightning bolt is one of nature’s most over-the-top phenomena, rarely failing to elicit at least a ping of awe no matter how many times a person has witnessed one. With his iconic kite-and-key experiments in the mid-18th century, Benjamin Franklin showed that lightning is an electrical phenomenon, and since then the general view has been that lightning bolts are big honking sparks no different in kind from the little ones generated by walking in socks across a carpeted room.

But scientists recently discovered something mind-bending about lightning: Sometimes its flashes are invisible, just sudden pulses of unexpectedly powerful radiation. It’s what Joseph Dwyer, a lightning researcher at the Florida Institute of Technology, has termed dark lightning.

Unknown to Franklin but now clear to a growing roster of lightning researchers and astronomers is that along with bright thunderbolts, thunderstorms unleash sprays of X-rays and even intense bursts of gamma rays, a form of radiation normally associated with such cosmic spectacles as collapsing stars. The radiation in these invisible blasts can carry a million times as much energy as the radiation in visible lightning, but that energy dissipates quickly in all directions rather than remaining in a stiletto-like lightning bolt.

Dark lightning appears sometimes to compete with normal lightning as a way for thunderstorms to vent the electrical energy that gets pent up inside their roiling interiors, Dwyer says. Unlike with regular lightning, though, people struck by dark lightning, most likely while flying in an airplane, would not get hurt. But according to Dwyer’s calculations, they might receive in an instant the maximum safe lifetime dose of ionizing radiation — the kind that wreaks the most havoc on the human body.

The only way to determine whether an airplane had been struck by dark lightning, Dwyer says, “would be to use a radiation detector. Right in the middle of [a flash], a very brief bluish-purple glow around the plane might be perceptible. Inside an aircraft, a passenger would probably not be able to feel or hear much of anything, but the radiation dose could be significant.”

However, because there’s only about one dark lightning occurrence for every thousand visible flashes and because pilots take great pains to avoid thunderstorms, Dwyer says, the risk of injury is quite limited. No one knows for sure if anyone has ever been hit by dark lightning.

About 25 million visible thunderbolts hit the United States every year, killing about 30 people and many farm animals, says John Jensenius, a lightning safety specialist with the National Weather Service in Gray, Maine. Worldwide, thunderstorms produce about a billion or so lightning bolts annually.

Read the entire article after the jump.

Image: Lightning in Foshan, China. Courtesy of Telegraph.