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\nAustralia\u2019s unprecedented wildfires are supercharged thanks to climate change, the type of trees catching fire and weather, experts say.<\/p>\n
\nAnd these fires are so extreme that they are triggering their own thunderstorms.<\/p>\n
\nHere are a few questions and answers about the science behind the Australian wildfires that so far have burned about 5 million hectares (12.35 million acres), killing at least 17 people and destroying more than 1,400 homes.<\/p>\n
\n\u201cThey are basically just in a horrific convergence of events,\u201d said Stanford University environmental studies director Chris Field, who chaired an international scientific report on climate change and extreme events. He said this is one of the worst, if not the worst, climate change extreme events he\u2019s seen.<\/p>\n
\n\u201cThere is something just intrinsically terrifying about these big wildfires. They go on for so long, the sense of hopelessness that they instill,\u201d Field said. \u201cThe wildfires are kind of the iconic representation of climate change impacts.\u201d<\/p>\n
\nQ: IS CLIMATE CHANGE REALLY A FACTOR? <\/p>\n
\nA: Scientists, both those who study fire and those who study climate, say there\u2019s no doubt man-made global warming has been a big part, but not the only part, of the fires.<\/p>\n
\nLast year in Australia was the hottest and driest on record, with the average annual temperature 2.7 degrees Fahrenheit (1.5 degrees Celsius) above the 1960 to 1990 average, according to Australia\u2019s Bureau of Meteorology. Temperatures in Australia last month hit 121.8 F (49.9 C).<\/p>\n
\n\u201cWhat would have been a bad fire season was made worse by the background drying\/warming trend,\u2019\u2019 Andrew Watkins, head of long-range forecasts at Australia\u2019s Bureau of Meteorology, said in an email.<\/p>\n
\nMike Flannigan, a fire scientist at the University of Alberta in Canada, said Australia\u2019s fires are \u201can example of climate change.\u201d<\/p>\n
\nA 2019 Australian government brief report on wildfires and climate change said, \u201cHuman-caused climate change has resulted in more dangerous weather conditions for bushfires in recent decades for many regions of Australia.\u201d<\/p>\n
\nQ: HOW DOES CLIMATE CHANGE MAKE THESE FIRES WORSE? <\/p>\n
\nA: The drier the fuel \u2014 trees and plants \u2014 the easier it is for fires to start and the hotter and nastier they get, Flannigan said.<\/p>\n
\n\u201cIt means more fuel is available to burn, which means higher intensity fires, which makes it more difficult \u2014 or impossible \u2014 to put out,\u201d Flannigan said.<\/p>\n
\nThe heat makes the fuel drier, so they combine for something called fire weather. And that determines \u201cfuel moisture,\u201d which is crucial for fire spread. The lower the moisture, the more likely Australian fires start and spread from lightning and human-caused ignition, a 2016 study found.<\/p>\n
\nThere\u2019s been a 10% long-term drying trend in Australia\u2019s southeast and 15% long-term drying trend in the country\u2019s southwest, Watkins said. When added to a degree of warming and a generally southward shift of weather systems, that means a generally drier landscape.<\/p>\n
\nAustralia\u2019s drought since late 2017 \u201chas been at least the equal of our worst drought in 1902,\u201d Australia\u2019s Watkins said. \u201cIt has probably been driven by ocean temperature patterns in the Indian Ocean and the long term drying trend.\u201d<\/p>\n
\nQ: HAS AUSTRALIA’S FIRE SEASON CHANGED? <\/p>\n
\nA: Yes. It\u2019s about two to four months longer, starting earlier especially in the south and east, Watkins said.<\/p>\n
\n\u201cThe fires over the last three months are unprecedented in their timing and severity, started earlier in spring and covered a wider area across many parts of Australia,\u201d said David Karoly, leader of climate change hub at Australia’s National Environmental science Program. \u201cThe normal peak fire season is later in summer and we are yet to have that.\u201d<\/p>\n
\nQ: IS WEATHER, NOT JUST LONG-TERM CLIMATE, A FACTOR?<\/p>\n
\nA: Yes. In September, Antarctica\u2019s sudden stratospheric warming \u2014 sort of the southern equivalent of the polar vortex \u2014 changed weather conditions so that Australia\u2019s normal weather systems are farther north than usual, Watkins said.<\/p>\n
\nThat means since mid-October there were persistent strong westerly winds bringing hot dry air from the interior to the coast, making the fire weather even riskier for the coasts.<\/p>\n
\n\u201cWith such a dry environment, many fires were started by dry lightning events (storms that brought lightning but limited rainfall),\u201d Watkins said.<\/p>\n
\nQ: ARE PEOPLE STARTING THESE FIRES? IS IT ARSON? <\/p>\n
\nA: It\u2019s too early to tell the precise cause of ignition because the fires are so recent and officials are spending time fighting them, Flannigan said.<\/p>\n
\nWhile people are a big factor in causing fires in Australia, it\u2019s usually accidental, from cars and trucks and power lines, Flannigan said. Usually discarded cigarettes don\u2019t trigger big fires, but when conditions are so dry, they can, he said.<\/p>\n
\nQ: ARE THESE FIRES TRIGGERING THUNDERSTORMS?<\/p>\n
\nA: Yes. It\u2019s an explosive storm called pyrocumulonimbus and it can inject particles as high as 10 miles into the air.<\/p>\n
\nDuring a fire, heat and moisture from the plants are released, even when the fuel is relatively dry. Warm air is less dense than cold air so it rises, releasing the moisture and forming a cloud that lifts and ends up a thunderstorm started by fire. It happens from time to time in Australia and other parts of the world, including Canada, Flannigan said.<\/p>\n
\n\u201cThese can be deadly, dangerous, erratic and unpredictable,\u201d he said.<\/p>\n
\nQ: ARE THE AUSTRALIAN TREES PRONE TO BURNING? <\/p>\n
\nA: Eucalyptus trees are especially flammable, \u201clike gasoline on a tree,\u201d Flannigan said. Chemicals in them make them catch fire easier, spread to the tops of trees and get more intense. Eucalyptus trees were a big factor in 2017 fires in Portugal that killed 66 people, he said.<\/p>\n
\nQ: HOW CAN YOU FIGHT THESE HUGE AUSTRALIA FIRES?<\/p>\n
\nA: You don\u2019t. They\u2019re just going to burn in many places until they hit the beach, Flannigan said.<\/p>\n
\n\u201cThis level of intensity, direct attack is useless,\u201d Flannigan said. \u201cYou just have to get out of the way… It really is spitting on a campfire. It\u2019s not doing any good.\u201d<\/p>\n
\nQ: WHAT’S THE LONG-TERM FIRE FUTURE LOOK LIKE FOR AUSTRALIA? <\/p>\n
\nA: \u201cThe extreme fire season in Australia in 2019 was predicted,\u201d said Australian National University climate scientist Nerilie Abram. \u201cThe question that we need to ask is how much worse are we willing to let this get? This is what global warming of just over 1 degree C looks like. Do we really want to see the impacts of 3 degrees or more are like, because that is the trajectory we are on.\u201d<\/p>\n
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\nFollow Seth Borenstein on Twitter at @borenbears .<\/p>\n
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\nThe Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute\u2019s Department of Science Education. The AP is solely responsible for all content.<\/p>\n<\/div>\n