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Extreme weather: What is it and how is it connected to climate change? Extreme weather: What is it and how is it connected to climate change?
(8 months later)
Heatwaves, deadly floods and wildfires - this summer people are having to confront the link between extreme weather and climate change. People around the globe are experiencing dramatic heatwaves, deadly floods and wildfires as a result of climate change.
Emissions from the burning of fossil fuels have been trapping heat in the atmosphere since the start of the industrial era. As a consequence, average temperatures have risen by 1.2C. Parts of Pakistan and north-west India could see temperatures of more than 50C this weekend.
This additional energy is unevenly distributed and bursts out in extremes like the ones we've been seeing this summer. Without reductions in global emissions, this cycle will keep going. Emissions from the burning of fossil fuels have been trapping heat in the atmosphere since the start of the industrial era. As a consequence, average temperatures have risen by 1.1C.
This additional energy is unevenly distributed and bursts out in extremes like those we're seeing at the moment. Without reductions in global emissions, this cycle will keep going.
Here are four ways climate change is contributing to extreme weather.Here are four ways climate change is contributing to extreme weather.
1. Hotter, longer heatwaves1. Hotter, longer heatwaves
To understand the impact of small changes to average temperatures, you need to to think of them as a bell curve, with extreme cold and hot at either end, and the bulk of temperatures in the middle. A small shift in the centre means that more of the curve touches the the extremes - and so heatwaves become more frequent and extreme. To understand the impact of small changes to average temperatures - think of them as a bell curve with extreme cold and hot at either end and the bulk of temperatures in the middle. A small shift in the centre means more of the curve touches the extremes - and so heatwaves become more frequent and extreme.
In the UK, warm spells have more than doubled in length in the past 50 years, according to the Met Office. In the UK, the Met Office says that warm spells have more than doubled in length in the past 50 years.
But the record heatwaves in Western Canada and the US were made longer and more intense by another weather phenomenon - a heat dome. Heatwaves can be made longer and more intense by another weather phenomenon - a heat dome.
Weeks ago, a Pacific storm, fuelled by warmer-than-normal sea temperatures, disrupted the jet stream. When a storm distorts the jet stream, which is made of currents of fast-flowing air, it is a bit like yanking a long skipping rope at one end and seeing the ripples transferring along it.
These waves cause everything to slow drastically and weather systems can become stuck over the same areas for days on end.
In an area of high pressure, hot air is pushed down and trapped in place, causing temperatures to soar over an entire continent.In an area of high pressure, hot air is pushed down and trapped in place, causing temperatures to soar over an entire continent.
In Lytton, Western Canada, temperatures hit 49.6C, breaking the previous record by almost 5C. Such an intense heatwave would have been virtually impossible without climate change, according to the World Weather Attribution network. When a storm distorts the jet stream, which is made of currents of fast-flowing air, it is a bit like yanking a skipping rope at one end and seeing the ripples move along it.
One theory is higher temperatures in the Arctic are causing the jet stream to slow down, increasing the likelihood of heat domes. These waves cause everything to slow drastically - and weather systems can become stuck over the same areas for days on end.
And exceptional heat has not been limited to North America this summer. In Russia, a heatwave sent temperatures soaring - matching a 120-year record. Northern Ireland broke its temperature record three times in the same week, while a new high was set in the Antarctic continent. This same type of stuck weather pattern is also responsible for the record warmth being experienced in India and Pakistan. Persistent high pressure and lower than normal rainfall lead to India's hottest March since records began 122 years ago.
Karachi, Pakistan, also notched up its hottest March day and night, amid the country's hottest March on record. As the heatwave built through April, Pakistan again saw records tumble. Jacobabad registered 49C at one point - with central and northwest India also experiencing a record-breaking month.
The UK Met office has warned that temperatures could break through 50C in parts of the region this weekend, and could rise even further towards the end of next week. These levels are about 5-7C above average for the time of year.
India issues extreme heatwave warning
Life where it's too hot to work, too hot to sleep
In the Southern Hemisphere, Argentina, Uruguay, Paraguay and Brazil all saw an historic heatwave in January - many areas reported their hottest day on record. In the same month, Onslow in Western Australia hit 50.7C, the joint-highest temperature ever reliably recorded in the Southern Hemisphere.
Last year, North America saw was hit by long heatwaves. In Lytton, Western Canada, temperatures hit 49.6C, breaking the previous record by almost 5C. Such an intense heatwave would have been virtually impossible without climate change, says the World Weather Attribution network.
One theory is higher temperatures in the Arctic are causing the jet stream to slow, increasing the likelihood of heat domes.
2. More persistent droughts2. More persistent droughts
As heatwaves become more intense and longer, droughts can worsen.As heatwaves become more intense and longer, droughts can worsen.
Less rain falls between heatwaves, so ground moisture and water supplies run dry more quickly. Less rain falls between heatwaves, so ground moisture and water supplies run dry more quickly. This means the ground heats up more quickly, warming the air above and leading to more intense heat.
And this in turn means the ground heats up more quickly, warming the air above and leading to more intense heat. Drought in Somalia - the country has now suffered three failed rainy seasons in a row
Demand for water from humans and farming puts even more stress on water supply, adding to water shortages. Demand for water from humans and farming puts even more stress on water supply, adding to shortages.
And by mid-July, following the early summer heatwaves, more than a quarter of US land was experiencing "extreme" or "exceptional" drought.
3. More fuel for wildfires3. More fuel for wildfires
Wildfires can be sparked by direct human involvement - but natural factors can play a huge part. Wildfires can be sparked by direct human involvement - but natural factors can also play a huge part.
The cycle of extreme and long-lasting heat caused by climate change draws more and more moisture out of the ground and vegetation.The cycle of extreme and long-lasting heat caused by climate change draws more and more moisture out of the ground and vegetation.
And these tinder-dry conditions provide fuel for fires, which can spread at an incredible speed. These tinder-dry conditions provide fuel for fires, which can spread at an incredible speed.
The impact of the heatwave on fire development was seen in an explosive fashion in western Canada this summer. A firefighting aircraft tackling a wildfire in Slovenia last month
This summer wildfires also tore through forests in southern Turkey, leaving the land scorched The Northern Hemisphere's wildfire season has begun early in some areas, due to lack of rainfall and unseasonable warmth. Fires have already ripped through parts of Siberia and Alaska, and unusually early fires have been reported in the likes of western Norway and the UK.
Fires developed so rapidly and explosively they created their own weather system, as pyrocumulonimbus clouds formed. In Canada last summer, heatwaves lead to fires that developed so rapidly and explosively they created their own weather system, as pyrocumulonimbus clouds formed. And these colossal clouds produced lightning, igniting more fires.
And these colossal clouds produced lightning, igniting more fires. The rising heat from intense wildfires can create massive, powerful clouds that produce their own weather
This same story is being repeated in Siberia.
The frequency of large wildfires has increased dramatically in recent decades.The frequency of large wildfires has increased dramatically in recent decades.
Compared with the 1970s, fires larger than 10,000 acres (40 sq km) are now seven times more common in western America, according to Climate Central, an independent organisation of scientists and journalists.Compared with the 1970s, fires larger than 10,000 acres (40 sq km) are now seven times more common in western America, according to Climate Central, an independent organisation of scientists and journalists.
Then and now: The burning issue of wildfiresThen and now: The burning issue of wildfires
How do wildfires start?How do wildfires start?
4. More extreme rainfall events4. More extreme rainfall events
In the usual weather cycle, hot weather creates moisture and water vapour in the air, which turns into droplets to create rain.In the usual weather cycle, hot weather creates moisture and water vapour in the air, which turns into droplets to create rain.
The warmer it becomes, however, the more vapour there is in the atmosphere, resulting in more droplets - and heavier rainfall, sometimes in a shorter space of time and over a smaller area.The warmer it becomes, however, the more vapour there is in the atmosphere, resulting in more droplets - and heavier rainfall, sometimes in a shorter space of time and over a smaller area.
Historic flooding in China, Germany, Belgium and the Netherlands has shown the devastating impact extreme rainfall events can have. Already this year, floods have hit Spain and also parts of eastern Australia. In a period of just six days Brisbane saw almost 80% of its annual rainfall, while Sydney recorded more than its average annual rainfall in little over three months.
And these rainfall events are connected to the impacts of climate change elsewhere, according to Peter Gleick, a water specialist from the US National Academy of Sciences. This video can not be played
"When areas of drought grow, like in Siberia and western US, that water falls elsewhere, in a smaller area, worsening flooding, like Germany and Belgium," he says. To play this video you need to enable JavaScript in your browser.
Watch: Record-breaking floods hit Spain’s east coast
These rainfall events are connected to the effects of climate change elsewhere, according to Peter Gleick, a water specialist from the US National Academy of Sciences.
"When areas of drought grow, like in Siberia and western US, that water falls elsewhere, in a smaller area, worsening flooding," he says.
The weather across the globe will always be highly variable - but climate change is making that more extreme.The weather across the globe will always be highly variable - but climate change is making that more extreme.
And the challenge now is not only limiting the further impact people have on the atmosphere but also adapting to and tackling the extremes we are already facing.And the challenge now is not only limiting the further impact people have on the atmosphere but also adapting to and tackling the extremes we are already facing.
Top image from Getty Images. Climate stripes visualisation courtesy of Prof Ed Hawkins and University of Reading.