Query: Past Australian droughts occurred when global temperatures were lower than now and wetter years occurred when such temperatures were rising.

Relevant passages:
Bushfires in Australia <=SEP=> Bushfires in Australia are frequent events during the warmer months of the year , due to Australia 's mostly hot , dry climate . Each year , such fires impact extensive areas . On one hand , they can cause property damage and loss of human life . On the other hand , certain native flora in Australia have evolved to rely on bushfires as a means of reproduction , and fire events are an interwoven and an essential part of the ecology of the continent . For thousands of years , Indigenous Australians have used fire to foster grasslands for hunting and to clear tracks through dense vegetation .   Major firestorms that result in severe loss of life are often named based on the day on which they occur , such as Ash Wednesday and Black Saturday . Some of the most intense , extensive and deadly bushfires commonly occur during droughts and heat waves , such as the 2009 Southern Australia heat wave , which precipitated the conditions during the 2009 Black Saturday bushfires in which 173 people lost their lives . Other major conflagrations include the 1983 Ash Wednesday bushfires , the 2003 Eastern Victorian alpine bushfires and the 2006 December Bushfires .   Global warming is increasing the frequency and severity of bushfires .

El Niño–Southern Oscillation <=SEP=> El Niño -- Southern Oscillation ( ENSO ) is an irregularly periodical variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean , affecting much of the tropics and subtropics . The warming phase is known as El Niño and the cooling phase as La Niña . Southern Oscillation is the accompanying atmospheric component , coupled with the sea temperature change : El Niño is accompanied with high , and La Niña with low air surface pressure in the tropical western Pacific . The two periods last several months each ( typically occur every few years ) and their effects vary in intensity .   The two phases relate to the Walker circulation , discovered by Gilbert Walker during the early twentieth century . The Walker circulation is caused by the pressure gradient force that results from a high pressure system over the eastern Pacific Ocean , and a low pressure system over Indonesia . When the Walker circulation weakens or reverses , an El Niño results , causing the ocean surface to be warmer than average , as upwelling of cold water occurs less or not at all . An especially strong Walker circulation causes a La Niña , resulting in cooler ocean temperatures due to increased upwelling .   Mechanisms that cause the oscillation remain under study . The extremes of this climate pattern 's oscillations cause extreme weather ( such as floods and droughts ) in many regions of the world . Developing countries dependent upon agriculture and fishing , particularly those bordering the Pacific Ocean , are the most affected .

2019–20 Australian bushfire season <=SEP=> The 2019–20 Australian bushfire season, colloquially known as Black Summer, was a period of unusually intense bushfires in many parts of Australia. In June 2019, the Queensland Fire and Emergency Service acting director warned of the potential for an early start to the bushfire season which normally starts in August. The warning was based on the Northern Australia bushfire seasonal outlook noting exceptional dry conditions and a lack of soil moisture, combined with early fires in central Queensland. Throughout the summer, hundreds of fires burnt, mainly in the southeast of the country. The major fires peaked during December–January. As of 9 March 2020, the fires burnt an estimated 18.6 million hectares (46 million acres; 186,000 square kilometres; 72,000 square miles), destroyed over 5,900 buildings (including 2,779 homes) and killed at least 34 people. Nearly three billion terrestrial vertebrates alone – the vast majority being reptiles – were affected and some endangered species were believed to be driven to extinction. At its peak, air quality dropped to hazardous levels in all southern and eastern states. The cost of dealing with the bushfires is expected to exceed the A$4.4 billion of the 2009 Black Saturday fires, and tourism sector revenues fell by more than A$1 billion. However, economists estimated that the Australian bushfires may cost over A$103 billion in property damage and economic losses, making the bushfires Australia's costliest natural disaster to date. Nearly 80 percent of Australians were affected either directly or indirectly by the bushfires.  By 7 January 2020, the smoke had moved approximately 11,000 kilometres (6,800 mi) across the South Pacific Ocean to Chile and Argentina. As of 2 January 2020, NASA estimated that 306 million tonnes (337 million short tons) of CO2 had been emitted.From September 2019 to March 2020, fires heavily impacted various regions of the state of New South Wales. In eastern and north-eastern Victoria large areas of forest burnt out of control for four weeks before the fires emerged from the forests in late December. Multiple states of emergency were declared across New South Wales, Victoria, and the Australian Capital Territory. Reinforcements from all over Australia were called in to assist fighting the fires and relieve exhausted local crews in New South Wales. The Australian Defence Force was mobilised to provide air support to the firefighting effort and to provide manpower and logistical support. Firefighters, supplies and equipment from Canada, New Zealand, Singapore and the United States, among others, helped fight the fires, especially in New South Wales.During the ensuing crisis, an air tanker and two helicopters crashed during firefighting operations, the air tanker crash resulting in the deaths of the three crew. Two fire trucks were caught in fatal incidents caused directly by fire conditions, killing three fire fighters.By 4 March 2020, all fires in New South Wales had been extinguished completely (to the point where there were no fires in the state for the first time since July 2019), and the Victoria fires had all been contained. The last fire of the season occurred in Lake Clifton, Western Australia, in early May.There has been considerable debate regarding the underlying cause of the intensity and scale of the fires, including the role of fire management practices and climate change, which during the peak of the crisis attracted significant international attention. Politicians visiting fire impacted areas received mixed responses, in particular Prime Minister Scott Morrison. An estimated A$500 million was donated by the public at large, international organisations, public figures and celebrities for victim relief and wildlife recovery. Convoys of donated food, clothing and livestock feed were sent to affected areas.

Global warming <=SEP=> Global warming , also referred to as climate change , is the observed century-scale rise in the average temperature of the Earth 's climate system and its related effects . Multiple lines of scientific evidence show that the climate system is warming . Many of the observed changes since the 1950s are unprecedented in the instrumental temperature record which extends back to the mid 19th century , and in paleoclimate proxy records over thousands of years .   In 2013 , the Intergovernmental Panel on Climate Change ( IPCC ) Fifth Assessment Report concluded that `` It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century . '' The largest human influence has been emission of greenhouse gases such as carbon dioxide , methane and nitrous oxide . Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to for their lowest emissions scenario and 2.6 to for the highest emissions scenario . These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing .   Future climate change and associated impacts will differ from region to region around the globe . Anticipated effects include warming global temperature , rising sea levels , changing precipitation , and expansion of deserts in the subtropics . Warming is expected to be greater over land than over the oceans and greatest in the Arctic , with the continuing retreat of glaciers , permafrost and sea ice . Other likely changes include more frequent extreme weather events including heat waves , droughts , heavy rainfall with floods and heavy snowfall ; ocean acidification ; and species extinctions due to shifting temperature regimes . Effects significant to humans include the threat to food security from decreasing crop yields and the abandonment of populated areas due to rising sea levels . Because the climate system has a large `` inertia '' and greenhouse gases will stay in the atmosphere for a long time , many of these effects will not only exist for decades or centuries , but will persist for tens of thousands of years .   Possible societal responses to global warming include mitigation by emissions reduction , adaptation to its effects , building systems resilient to its effects , and possible future climate engineering . Most countries are parties to the United Nations Framework Convention on Climate Change ( UNFCCC ) ,  whose ultimate objective is to prevent dangerous anthropogenic climate change . Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 C-change relative to pre-industrial levels , with efforts made to limit warming to 1.5 C-change .   Public reactions to global warming and concern about its effects are also increasing . A global 2015 Pew Research Center report showed a median of 54 % consider it `` a very serious problem '' . There are significant regional differences , with Americans and Chinese ( whose economies are responsible for the greatest annual CO2 emissions ) among the least concerned .

Effects of global warming on human health <=SEP=> The effects of global warming include effects on human health . The observed and projected increased frequency and severity of climate related impacts will further exacerbate the effects on human health . This article describes some of those effects on individuals and populations .