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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?
(7 days later)
People around the globe are experiencing dramatic heatwaves, deadly floods and wildfires as a result of climate change.People around the globe are experiencing dramatic heatwaves, deadly floods and wildfires as a result of climate change.
Parts of Pakistan and north-west India could see temperatures of more than 50C this weekend. The UK and parts of Europe have seen temperatures of above 40C this month, leading to transport disruption and water shortages.
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. Emissions caused by the burning of fossil fuels have been trapping heat in the atmosphere since the start of the industrial era. This extra heat isn't evenly distributed across the globe, and bursts out extreme weather events.
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. Unless global emissions are cut, this cycle will continue.
Here are four ways climate change is contributing to extreme weather. Here are four ways climate change is changing the weather.
1. Hotter, longer heatwaves1. Hotter, longer heatwaves
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. 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.
In the UK, the Met Office says that warm spells have more than doubled in length in the past 50 years. A small shift in the centre means more of the curve touches the extremes - and so heatwaves become more frequent and extreme.
Temperatures in the UK topped 40C for the first time on 19 July.
The Met Office estimates that the extreme heat seen during the most recent heatwave is ten times more likely now because of climate change. And things could worsen.
"In a few decades this might actually be a quite a cool summer," says Professor Friederike Otto, a climate scientist at Imperial College London.
The Met Office has also pointed out that heatwaves are not just hotter: They're also lasting longer. Warm spells have more than doubled in length in the past 50 years.
Why is it so hot in the UK?
Is the UK getting hotter?
Heatwaves can be 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.
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.
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.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.
These waves cause everything to slow drastically - and weather systems can become stuck over the same areas for days on end. These waves cause everything to slow drastically and weather systems can become stuck over the same areas for days on end - as was seen in India earlier this year.
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. India and Pakistan have already faced five successive heatwaves this year, with Jacobabad, in Pakistan, registering 49C at one point in May.
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. In the Southern Hemisphere, Argentina, Uruguay, Paraguay and Brazil all saw an historic heatwave in January - many areas reported their hottest day on record.
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. In the same month, Onslow in Western Australia hit 50.7C, the joint-highest temperature ever reliably recorded in the Southern Hemisphere.
India issues extreme heatwave warning Last year, North America was also hit by long heatwaves. The western Canadian town of Lytton burnt down when temperatures hit 49.6C, breaking the previous record by almost 5C.
Life where it's too hot to work, too hot to sleep Such an intense heatwave would have been virtually impossible without climate change, says the World Weather Attribution network, a collaboration between international climate scientists.
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. One theory suggests higher temperatures in the Arctic are causing the jet stream to slow, increasing the likelihood of heat domes.
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. Life at 50 degrees
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 also worsen.
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. Less rain falls between heatwaves, so ground moisture and water supplies run dry more quickly. This means the ground takes less time to heat up, 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 Drought in Somalia - the country has suffered three failed rainy seasons in a row
Demand for water from humans and farming puts even more stress on water supply, adding to shortages.Demand for water from humans and farming puts even more stress on water supply, adding to shortages.
3. More fuel for wildfires3. More fuel for wildfires
Wildfires can be sparked by direct human involvement - but natural factors can also 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.
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.
A firefighting aircraft tackling a wildfire in Slovenia last month A firefighting aircraft tackling a wildfire in Slovenia in March
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. The Northern Hemisphere's wildfire season begun early in some areas, due to lack of rainfall and unseasonable warmth, and has worsened through July.
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. Most recently severe wildfires have been reported in France, Spain, Portugal, Greece, Croatia and Albania - with thousands of residents evacuated and several hundreds reported to have died.
The rising heat from intense wildfires can create massive, powerful clouds that produce their own weather More than 10,000 residents and tourists have been evacuated in France since the start of July
In Canada last summer, heatwaves led to fires which developed so rapidly and explosively that they created their own weather system, forming pyrocumulonimbus clouds. These colossal clouds then produced lightning, igniting more fires.
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. This results in more droplets and heavier rainfall, sometimes in a shorter space of time and over a smaller area.
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.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.
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Watch: Record-breaking floods hit Spain’s east coastWatch: Record-breaking floods hit Spain’s east coast
Watch: Record-breaking floods hit Spain’s east coastWatch: 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.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."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 those variations 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.