Newly identified jet-stream pattern could imperil global food supplies

Newly identified jet-stream pattern could imperil global food supplies

SOURCE: Phys.org DATE: December 9, 2019 SNIP: Scientists have identified systematic meanders in the globe-circling northern jet stream that have caused simultaneous crop-damaging heat waves in widely separated breadbasket regions-a previously unquantified threat to global food production that, they say, could worsen with global warming. The research shows that certain kinds of waves in the atmospheric circulation can become amplified and then lock in place for extended periods, triggering the concurrent heat waves. Affected parts of North America, Europe and Asia together produce a quarter of the world food supply. The study appears this week in the journal Nature Climate Change. “We found a 20-fold increase in the risk of simultaneous heat waves in major crop-producing regions when these global-scale wind patterns are in place,” said lead author Kai Kornhuber, a postdoctoral researcher at Columbia University’s Earth Institute. “Until now, this was an underexplored vulnerability in the food system. During these events there actually is a global structure in the otherwise quite chaotic circulation. The bell can ring in multiple regions at once.” Kornhuber warned that the heat waves will almost certainly become worse in coming decades, as the world continues to warm. The meanders that cause them could also potentially become more pronounced, though this is less certain. Because food commodities are increasingly traded on a global scale, either effect could lead to food shortages even in regions far from those directly affected by heat waves. The jet stream is a fast-moving river of air that continuously circles the northern hemisphere from west to east. It generally confines itself to a relatively narrow band, but can meander north...
Summer weather is getting ‘stuck’ due to Arctic warming

Summer weather is getting ‘stuck’ due to Arctic warming

SOURCE: The Guardian DATE: August 20, 2018 SNIP: Summer weather patterns are increasingly likely to stall in Europe, North America and parts of Asia, according to a new climate study that explains why Arctic warming is making heatwaves elsewhere more persistent and dangerous. Rising temperatures in the Arctic have slowed the circulation of the jet stream and other giant planetary winds, says the paper, which means high and low pressure fronts are getting stuck and weather is less able to moderate itself. The authors of the research, published in Nature Communications on Monday, warn this could lead to “very extreme extremes”, which occur when abnormally high temperatures linger for an unusually prolonged period, turning sunny days into heat waves, tinder-dry conditions into wildfires, and rains into floods. Circulation stalling has long been a concern of climate scientists, though most previous studies have looked at winter patterns. The new paper reviews research on summer trends, where it says there is mounting evidence of planetary wind systems – both low-level storm tracks and higher waves in the troposphere – losing their ability to shift the weather. One cause is a weakening of the temperature gradient between the Arctic and Equator as a result of man-made greenhouse gas emissions. The far north of the Earth is warming two to four times faster than the global average, says the paper, which means there is a declining temperature gap with the central belt of the planet. As this ramp flattens, winds struggle to build up sufficient energy and speed to push around pressure systems in the area between them. As a result, there is...
Europe’s freak weather, explained

Europe’s freak weather, explained

SOURCE: Politico DATE: August 16, 2018 SNIP: We’ve all become increasingly used to reports of extreme weather over the past few years. But this summer’s raft of dramatic weather events is significant: Not only does it show what warming can do, it points to the potential large-scale trouble that lurks in the disruption of the planet’s winds and ocean currents. That global warming leads to more heat extremes is not rocket science and has been confirmed by global data analysis. We’re seeing five times more monthly heat records — such as “hottest July on record in California” — now than we would in a stable climate. It’s not just that the weather is doing what it always does, except at a higher temperature level. Rather, there is growing evidence that the dynamics of weather itself are changing. This is currently one of the hottest topics in climate research. The basic idea is that the jet stream — a band of high winds around the Northern Hemisphere that significantly influences our weather in the mid-latitudes — is changing. This phenomenon has been confirmed by data: Researchers showed in 2015 that the jet stream has actually slowed down significantly in recent decades and undulates more. The cause is probably the strong warming of the Arctic, as the jet stream is driven by the temperature contrast between the tropics and the Arctic. Because this temperature difference is getting smaller and smaller, the jet stream is weakening and becoming less stable. The weaker summer circulation means fewer weather changes, so the weather is becoming more persistent. But the atmosphere is not the only...
Extreme Heat Event in Northern Siberia and the coastal Arctic Ocean This Week

Extreme Heat Event in Northern Siberia and the coastal Arctic Ocean This Week

SOURCE: Ocean’s Wrath DATE: July 2, 2018 (updated July 9, 2018) SNIP: This isn’t typically what I would write about in this blog, as I typically cover threatening ocean storms. However, this has implications for the Arctic Ocean and possibly mid-latitude weather. An extreme heat event for this particular region…with high temperatures of greater than 40 degrees F (greater than 20 C) above recent normals…will impact the coast of the Arctic Ocean (specifically the Laptev Sea and Eastern Siberian Sea) Wednesday-Friday. This will generate maximum daily temperatures as high as 90-95 degrees (32-35 C) near the open ocean coast! Yes, you read that correctly. Needless to say, a true roasting for this area. In addition to the immediate impact on sea ice, there is also the impact on permafrost. Or perhaps, what was “permafrost”. More of these kind of intense heat events now hitting the Arctic at the height of summer will result in more rapid destruction of land permafrost as well as heating of the shallow waters just offshore where sub-sea permafrost is located, allowed for increasingly more carbon dioxide and methane to be released into the atmosphere, speeding up global warming and resulting climate change, including effects on storm patterns in the mid-latitudes. Read the update at the top of the original...
Warm Arctic? Expect Northeast Blizzards: What 7 Decades of Weather Data Show

Warm Arctic? Expect Northeast Blizzards: What 7 Decades of Weather Data Show

SOURCE: Inside Climate News DATE: March 13, 2018 SNIP: The warmer the Arctic, the more likely the Northeast will be clobbered by blizzards, says a team of researchers who analyzed winter weather patterns going back to 1950. Citing disruptive storms like Snowzilla (2016), Snowmaggedon (2010) and Snowpocalypse (2009), the climate scientists wrote that “heavy snowfalls are generally more frequent since 1990, and in many cities the most extreme snowfalls have occurred primarily during recent decades.” Their study, published in the journal Nature Communications, links the increased frequency of extreme winter storms with the rapid and persistent warming of the Arctic since around 1990. When temperatures over the Arctic spike, especially high in the atmosphere, extreme winter weather is two to four times more likely in Boston and New York, while the U.S. West tends to see warmer and drier conditions, they conclude. Jennifer Francis, a Rutgers University climate researcher and co-author of the study, said that while the study doesn’t show causation, the pattern they found reinforces other studies showing that the declining temperature contrast between the Arctic and the mid-latitudes leads to a wavier jet stream that disrupts normal weather...