Environment

How a Monster El Niño Transforms the World’s Weather

From crippling drought in southern Africa to a record number of February tornadoes in the U.S. Southeast, an exceptionally strong El Niño has been making headlines around the globe as it tampers with the world’s weather.

While the event has begun its slow decline, those wide-ranging impacts will continue to be felt for weeks and months to come — good news for those in California, who need El Niño-Fuelled rains, but bad news for the many areas, like Indonesia, which is suffering from deep drought, food and water shortages, and wildfires.

Already this year, El Niño-related weather has cost billions of dollars in damage and left some 100 million people facing food and water shortages.

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First, the big picture: El Niño is most known for shifting a large pool of warm ocean waters from the western to the central and eastern tropical Pacific. That shift changes where heat is pumped into the tropical atmosphere, disrupting its typical circulation patterns. Those local disruptions cause a domino effect through the global atmosphere that can alter weather thousands of miles away.

There are two main circulation patterns that are affected. All around the tropics is a pattern of rising and sinking air — like a vertical loop — called the Walker Circulation. The rising air corresponds to areas of unsettled, rainy weather, while the sinking air creates a stable, dry clime. Normally in the tropical Pacific, a major area of rising air is found over the western portions, where the warmest waters are found. With the eastward shift from El Niño, that rising air (and its sinking counterpart) move eastward as well. This displacement shifts the other branches of the Walker Circulation around the tropics, pushing wetter weather over areas that might normally be dry and vice versa. These areas typically see some of the strongest impacts from El Niño because they are in a region more directly linked to it.

The changes in the Walker Circulation in turn cause shifts in another looping pattern called the Hadley Circulation that runs north-to-south to the Walker’s east-to-west. And those changes in the Hadley Circulation can affect the subtropical jet stream — an area of fast-moving air that guides storms — in both the Northern and Southern hemispheres. This is how El Niño can affect regions far from the tropics.

The changes in these main circulation patterns interact with other factors, like seasonal monsoons and other major climate patterns, which is why none of the typical impacts associated with El Niño are guaranteed. It merely shifts the odds in their favour.

Environment

Climate Disasters Now Happening Daily: UN

Weather-related disasters have nearly doubled over the past 30 years — now occurring almost daily somewhere in the world, according to a new report.

Published by the United Nations Office for Disaster Risk Reduction (UNISDR), The Human Cost of Weather Related Disasters (PDF copy) fell short of directly blaming climate change for the increase.

But it did warn, “predictions of more extreme weather in the future almost certainly mean that we will witness a continued upward trend in weather-related disasters in the decades ahead.”

The report found that 600,000 people have died as a result of floods, storms, heatwaves, droughts and other weather-related events since 1995.

About 4.1 billion others being injured, left homeless or in need of emergency assistance.

There were an average of 335 weather-related disasters annually between 2005 and this year, up 14 percent from 1995 to 2004 and almost twice as many as during the years from 1985 to 1994.

The report ranked the United States, China, India, Philippines and Indonesia as being hit by the highest number of disasters.

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Global Warming

New Research Links Extreme Weather to Global Warming

A new study has been published by a team of climatologists possibly linking global warming to these extreme weather events.

The key to this is what’s called a “blocking pattern”, where a high-pressure system becomes immobile, squatting over a specific spot. Under the high-pressure spot, this can bring long, gruelling heat waves that don’t go away for days or weeks. On the edges it can bring a deluge of rain, as moist air from the south is brought up to meet colder air coming down from the north. That’s what Detroit and New York just went through.

These blocking patterns are themselves associated with the jet stream, the constant flow of air about 10 kilometres above sea level at latitudes between 30° and 60°. Sometimes the flow weakens, and the winds can dip down into more southern latitudes. These meanders (sometimes mistakenly called the “polar vortex”) depend on a lot of factors, but the new research just published indicates they may be due to the Arctic warming up. The physics is complicated — fluid dynamics is amazingly subtle and complex — but the research indicates a warming Arctic can create and amplify the conditions that lead to jet stream excursions, and therefore blocking patterns.

It was a blocking pattern that led to a phenomenal heat wave in Alaska in 2013, to the floods in the Northeast, and to the unbelievable rain we saw in Boulder, Colorado last year; they got over 30 cm in just a day.

Environment

Asian Pollution Boosts Pacific Storm Power

Pollution from China’s coal-burning power plants is pumping up winter storms over the northwest Pacific Ocean and changing North America’s weather, a new study finds.

Northwest Pacific winter storms are now 10 percent stronger than they were 30 years ago, before Asian countries began their industrial boom, according to research published today (April 14) in the Proceedings of the National Academy of Sciences.

North America will be hardest hit by the intensifying storms, which move from west to east, said lead study author Yuan Wang, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

Pollution from Asia is also changing weather patterns over North America, Wang added.

Wang said this winter’s unusually cold weather east of the Rocky Mountains could have been influenced by pollution-driven cyclones and high-pressure systems in the northern Pacific.

These Pacific weather patterns caused swoops in the jet stream that drove cold air south across the central and eastern United States — the so-called polar vortex. The same weather patterns are linked with record-high temperatures in Alaska this winter.

“This cold winter in the U.S. probably had something to do with stronger cyclones over the Pacific,” Wang said.

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Environment

Altering jet stream ‘may drive weather shift’

New research suggests that the main system that helps determine the weather over Northern Europe and North America may be changing. The study shows that the so-called jet stream has increasingly taken a longer, meandering path. This has resulted in weather remaining the same for more prolonged periods.

The meandering jet stream has accounted for the recent stormy weather over the UK and the bitter winter weather in the US Mid-West remaining longer than it otherwise would have. We can expect more of the same and we can expect it to happen more frequently. The jet stream, as its name suggests, is a high-speed air current in the atmosphere that brings with it the weather. It is fuelled partly by the temperature differential between the Arctic and the mid-latitudes.

Environment

Extreme Weather Hits Hard Worldwide

From unprecedented storms and flooding in the UK to severe drought in California and Brazil, 2014 has kicked off with some exceptional and weird weather events.

The UK is experiencing its most exceptional period of rainfall in 248 years, with hundreds of flood alert warnings covering much of the country and hundreds of home left inundated. The prolonged storms have played havoc across the country since December, with more than 130 severe flood risk warnings — meaning a potential threat to life — issued and more than 5,000 homes flooded. This week fourteen severe warnings remain in place, with no let up of the rain in sight.

Across the globe in Brazil, residents in Sao Paulo — South America’s largest city — are facing the opposite problem, as record heat and drought have sparked fears of water shortages. The city is on alert following warnings the system that provides half the its drinking water could run dry in the next 40 days. Like cities across Brazil, Sao Paulo is experiencing its worst drought in 50 years, with last month the hottest January on record. The combination of low precipitation and extreme heat right across the country are not only sparking fears of water shortages but also of crop damage and higher energy prices.

The Western U.S. is facing similar problems, as the state of California is in the grips of what is likely to be the region’s worst drought in 500 years. Low snowpack in the mountains are leaving the state’s creeks, rivers and reservoirs — which provide essential water and hydroelectric power for cities and the agricultural industry — dry, putting food prices at risk. Meanwhile, wildfires continue to plague the region at increased rates. Brazil and California aren’t the only places experiencing record drought and heat.

In Alaska, record high temperatures have triggered a series of extremely large avalanches, with debris piles more than 30-metres thick blocking off towns from highway access.

Stifling heat in Australia is also causing havoc, after the country suffered through its hottest January in 13 years — the fourth hottest on record. The dry and hot conditions have left scores of wildfires raging across southeast Australia, and are threatening the country’s agriculture production, as farmers struggle to provide water for their cattle and crops.

A slew of deadly flooding events are also hitting communities around the world. In Bolivia flooding and landslides have so far claimed 42 lives this year, while flooding in northern Indonesia has killed 13 people and driven tens of thousands more from their homes, and in Mozambique 11 people have been killed in flooding.

Extreme rainfall is also hitting countries across mainland Europe. Large parts of France and Italy are under flood alert, with hundreds of people being forced out of their homes. The heavy rain and flooding have also claimed three lives in Italy and two in France.

In Romania heavy snowfall has been the problem, blocking roads and railways across the country and leaving schools closed and thousands stranded both in their homes and on the roads. Cold weather has also been playing havoc in Slovenia, where trees, buildings and cars have been encased in thick ice, causing perilous conditions as power lines and tress tumbling to the ground. The government estimates that around 40 percent of the country’s forests have been damaged by the cold snap.

Environment

Trade Winds Declining in Hawaii

Experts say trade winds are declining, a drop that’s slowly changing life across the islands. Part of what makes living in Hawaii so pleasant is the gentle breeze. Arriving from the northeast, it’s light enough that it is barely noticeable but strong enough to chase away the humidity.

The effects of the decline in the trade winds can be seen from the relatively minor – such as residents unaccustomed to the humidity complaining about the weather and having to use their fans and air conditioning more often – to the more consequential – including winds being too weak to blow away volcanic smog. The winds also help bring the rains, and their decline means less water. It’s one reason officials are moving to restore the health of the mountainous forests that hold the state’s water supply and encourage water conservation. Scholars are studying ways for farmers to plant crops differently.

It’s not clear what’s behind the shift in the winds. A study has shown a decades-long decline, including a 28 per cent drop in northeast trade wind days at Honolulu’s airport since the early 1970s.

These days there are fewer waves to surf because the winds are arriving less often. Sometimes the winds are too weak to blow away the volcanic smog, or vog, created by sulfur dioxide erupting from Kilauea volcano on the Big Island, leaving a white or brownish haze hanging over Honolulu. This aggravates asthma and other respiratory problems.

For now, the most important consequence will be declining rainfall and a drop in the water supply, particularly as Hawaii’s population grows and uses more water. Trade winds deliver rain to Hawaii when clouds carried from the northeast hit mountainous islands built by millions of years of volcanic eruptions. These rains, together with rainfall from winter storms, are the state’s primary sources of water. On Oahu, the rain feeds ground aquifers that supply water to about 950,000 people in Honolulu and surrounding towns. Residents are reporting streams near their homes are flowing lower than before. Scientists don’t know if this is a downward trend or just the lower leg of a long-term cycle.

Environment

Arctic Ice Loss May Drive Extreme Weather Patterns

Several researchers say that warming conditions in the Arctic may be weakening jet stream currents and causing extreme weather systems to linger in northern mid-latitudes.

Climate scientists have blamed melting sea ice for causing extreme winter in North America and Europe during this winter. Thickness of the ice is also a concern among the environmental scientists.

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The jet stream is a band of very strong winds that blow from west to east, several miles above the earth’s surface. Normally, these powerful winds push weather systems around, preventing them from staying in one place for very long.

However, the loss of sea ice in recent decades has allowed Arctic waters to absorb more heat energy from the sun, which has in turn heated the atmosphere above the water.

This heating influences atmospheric pressure and appears to be slowing the westerly jet stream. Instead of flowing quickly and in a relatively straight line, like a river down a mountain, the winds mimic a slower, meandering river.

Arctic sea ice is referred to as the planet’s air conditioner, due to its influence on global temperatures. Last year, Arctic sea ice reached its lowest level in the satellite age.

This rate of sea ice loss is faster than what models predicted. Now, some experts say, the Arctic could experience a nearly ice-free summer by 2020.

Environment

Arctic sea ice is shrinking at a rate much faster than scientists ever predicted and its collapse, due to global warming, may well cause extreme weather this winter in North America and Europe.Decades ago, Arctic ice covered about 6 million square miles of sea in the winter, and would shrink to about 3 million square miles in the summer. The rate of summer melt increased enormously around 2005, however, and today scientists say Arctic ice covers only about 1 million square miles.

The loss of Arctic ice has several effects. Ice reflects heat and solar energy back into space. With less ice cover, that heat energy is instead absorbed by the ocean, which warms and melts more ice. Currently, the Arctic region is the fastest-warming region on the planet, and the change in temperature will probably influence weather patterns here and in Europe.

The heating and cooling of Arctic seawater has been affecting the jet stream – the river of air that flows from west to east high above the Earth’s surface – and has slowed it down, Francis said. The jet stream controls the formation and movement of storm systems, so when its movement slows, weather conditions persist for longer periods of time over the same area. They get “stuck.”