Wednesday, 30 November 2016

Global drought

With Temperatures Hitting 1.2 C Hotter than Pre-Industrial, Drought Now Spans the Globe



30 November, 2016

Jeff Goodell, an American author and editor at Rolling Stone, is noted for saying this: “once we deliberately start messing with the climate, we could inadvertantly shift rainfall patterns (climate models have shown that the Amazon is particularly vulnerable) causing collapse of ecosystems, drought, famine and more.”

We are in the process of testing that theory. In the case of drought, which used to just be a regional affair but has now gone global, Goodell appears to have been right on the money.
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According to a recent report by the World Meteorological Organization, the Earth is on track to hit 1.2 degrees Celsius hotter than pre-industrial temperatures during 2016. From sea-level rise, to melting polar ice, to extreme weather, to increasing numbers of displaced persons, this temperature jump is producing steadily worsening impacts. Among the more vivid of these is the current extent of global drought.

The Four-Year Global Drought

During El Nino years, drought conditions tend to expand through various regions as ocean surfaces heat up. From 2015 to 2016, the world experienced a powerful El Nino. However, despite the noted influence of this warming of surface waters in the Equatorial Pacific, widely expansive global drought extends back through 2013 and farther.
four-year-precipitation-anomalies-updated
(The Global Drought Monitor finds that dry conditions have been prevalent over much of the globe throughout the past four years. For some regions, like the Colorado River area, drought has already extended for more than a decade. Image source: SPEI Global Drought Monitor.)

In the above image, we see soil moisture deficits over the past 48 months. What we find is that large sections of pretty much every major continent are undergoing at least a four-year drought. Drought conditions were predicted by climate models to intensify in the middle latitudes as the world heated up. It appears that this is already the case, but the Equatorial zone and the higher latitudes are also experiencing widespread drought. If there is a detectable pattern in present conditions, it is that few regions have avoided drying. Drought is so wide-ranging as to be practically global in its extent.
Widespread Severe Impacts

These drought conditions have noted impacts.
In California alone, more than 102 million trees have died due to rising temperatures and a drought that has lasted since 2010. Of those, 62 million have perished just this year. Drought’s relationship to tree mortality is pretty simple — the longer drought lasts, the more trees perish as water stores in roots are used up. California has, so far, lost 2.5 percent of its live trees due to what is now the worst tree mortality event in the state’s history.
world-vegetative-health-index
(It’s not just California. Numerous regions around the world show plants undergoing life-threatening levels of stress. In the above map, vegetative health is shown to be moderately stressed [yellow] to severely stressed [pink] over broad regions of the world. Image source:Global Drought Information System.)

The California drought is just an aspect of a larger drought that encompasses much of the North American West. For the Colorado River area, this includes a 16-year-long drought that has pushed Lake Mead to its lowest levels ever recorded. With rationing of the river’s water supplies looming if a miraculous break in the drought doesn’t suddenly appear, states are scrambling to figure out how to manage a worsening scarcity. Meanwhile, reports indicate that cities like Phoenix will require executive action on the part of the President to ensure water supplies to millions of residents over the coming years, should conditions fail to improve.

Further east, drought has flickered on and off in the central and southern U.S.In the southeast, a flash drought has recently helped to spur an unseasonable spate of wildfires over the Smoky Mountain region. Yesterday, at Gaitlinburg, TN, raging flames fed by winds ahead of a cold front forced 14,000 people to evacuate, damaged or destroyed 100 homes, and took three lives.
siberian-wildfires-july-2016
(Siberian wildfires burning on July 23, 2016 occur in the context of severe drought. Image source: LANCE MODIS.)

In the upper northern latitudes, the primary upshot of drought has also been wildfires. Wildfires are often fanned by heat and drought in heavily forested regions that see reduced soil moisture levels. Thawing permafrost and reduced snow cover levels exacerbate the situation by further reducing moisture storage in dry regions and by adding peat-like fuels for fires.

From Alaska to Canada to Siberia, this has increasingly been the case. Last year, Alaska experienced one of its worst wildfire seasons on record. This year, both heat and drought contributed to the severe fires raging around the Fort McMurray region in Canada. And over recent years, wildfires running through a tremendously dry Siberia have been so extreme that satellites orbiting one million miles away could detect the smoke plumes.

Drought and wildfires in or near the Arctic justifiably seem odd, but when one considers the fact that many climate models had predicted that the higher northern latitudes would be one of the few major regions to experience increases in precipitation, that oddity turns ominous. If the present trend toward widespread Arctic drought is representative, then warming presents a drought issue from Equator to Pole.
A dwindling Lake Baikal — which feeds on water flowing in from rain and snow in Central Siberia — bears grim testament to an expanding drought over central and northern Russia. Lake Baikal, the world’s deepest and oldest lake, is threatened by climate change-related drying of the lands that drain into it. In 2015, water levels in Baikal hit record-low levels, and over the past few years, fires raging around the lake have increasingly endangered local communities and wildlife.
To the south and west, the Gansu province of China was placed under a level 4 drought alert this past summerThere, large swaths of crops were lost; half a billion dollars in damages mounted. The Chinese government rushed aid to 6.2 million affected residents, trucking potable water into regions rendered bereft of local supplies.
india-drought-baked-and-bleached-riverbeds
(Lakes and river beds dried up across India earlier this year as the monsoon was delayed for the third year in a row. Image source: India Water Portal.)

India this year experienced similar, but far more widespread, water shortages. In April, 330 million people within India experienced water stress. Water resupply trains wound through the countryside, delivering bottles of potable liquid to residents who’d lost access. A return of India’s monsoon provided some relief, but drought in India and Tibet’s highlands remains in place as glaciers shrink in the warming air.

Africa has recently seen various food crises crop up as wildfires raged through its equatorial forests. Stresses to humans, plants, and animals due to dryness, water and food shortage, and fires have been notably severe. Earlier this year, 36 million people across Africa faced hunger due to drought-related impacts. Nearer term, South Africa has been forced to cull hippo and buffalo herds as a multi-year drought continues there.

Shifting north into Europe, we also find widespread and expanding drought conditions. This situation is not unexpected for Southern Europe, where global climate models show incursions of desert climates from across the Mediterranean. But as with northern Russia and North America, Northern Europe is also experiencing drought. These droughts across Europe helped to spark severe wildfires in Portugal and Spain in the summer, as corn yields for the region are predicted to fall.
drought-wildfires-peru
(During November, drought spurred wildfires that erupted along the Amazon Rainforest’s boundary zone in Peru. Image source: LANCE MODIS.)

Finally finding our way back into the Americas, we see widespread drought conditions covering much of Brazil and Columbia, winding down the Andes Mountains through Peru, Bolivia, Chile, and Argentina. In sections of the increasingly clear-cut and fire-stricken Amazon Rainforest and running on into northeastern Brazil, drought conditions have now lasted for five years. There, half of the region’s cities face water rationing and more than 20 million people are currently confronted with water stress. From September to November 2015, more than 100,000 acres of drought-stricken Amazonian rainforest has burned in Peru. Meanwhile, Bolivia has seen its second-largest lake dry up and critical water-supplying glaciers melt as hundreds of thousands of people fall under water rationing.

Impacts to Food

Ongoing drought and extreme weather have created local impacts to food supplies in various regions. However, these impacts have not yet seriously affected global food markets. Drought in Brazil and India, for example, has significantly impacted sugar production, which in turn is pushing global food prices higher. Cereal production is a bit off which is also resulting in higher prices, though not the big jumps we see in sugar. But a Food and Agricultural Organization (FAO) Index for October of 2016 (173 approx) at 9 percent higher than last year’s measure for this time of year is still quite a ways off the 229 peak value during 2011 that helped to set off so much unrest around the globe.
food-index
(Rising food prices during 2016 in the face of relatively low energy prices and significant climate-related challenges to farmers is some cause for concern. Image source: FAO.)

That said, with energy prices falling into comparatively low ranges, relatively high (and rising) food prices are some cause for concern. Traditionally, falling energy prices also push food prices lower as production costs drop, but it appears that these gains by farmers are being offset by various environmental and climate impacts. Furthermore, though very widespread, drought appears to have thus far avoided large grain-producing regions like the central U.S., and central and east Asia. So the global food picture, if not entirely rosy, isn’t as bad as it could be.
Conditions in Context — Increasing Evaporation, Melting Glaciers, Less Snow Cover, Shifting Climate Zones

With the world now likely to hit 1.5 C above pre-industrial temperatures over the next 15 to 20 years, overall drought conditions will likely worsen. Higher rates of evaporation are a primary feature of warming, meaning more rain must fall just to keep pace. In addition, loss of glacial ice in various mountain ranges and loss of snow cover in drier Arctic and near-Arctic environments will further reduce river levels and soil moisture. Increasing prevalence of extreme rainfall events versus steady rainfall events will further stress the vegetation that aids in soil moisture capture. Finally, changes to atmospheric circulation due to polar amplification will combine with a poleward movement of climate zones to generally confuse traditional growing seasons. As a result, everything that relies on steady water supplies and predictable weather patterns will face challenges as the world shifts into a state of more obvious climate change.
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