From ScienceForSustainability
Jump to navigation Jump to search

Widespread and intense wildfires such as occurred in Australia in their summer/autumn of 2019-2020, and the western USA in summer/autumn 2020, have prompted debate about to what extent they are caused by climate change and how much by land and forest management practices such as the suppression of small wildfires, or lack of controlled burning, leading to build-up of flammable material.

The scientific consensus seems to be that both are factors, and whilst management practices contribute to many wildfires they do not fully explain them, and climate change effects are undoubtedly also a large factor.

A Sept 2020 ScienceBrief review "Climate change increases the risk of wildfires" by Adam J. P. Smith, Matthew W. Jones, John T. Abatzoglou, Josep G. Canadell, and Richard A. Betts, looking at 116 scientific articles, finds that

climate change increases the frequency and/or severity of fire weather – periods with a high fire risk due to a combination of high temperatures, low humidity, low rainfall and often high winds – in many regions around the world. The western United States is among the regions where the trends in fire weather have been most pronounced in the past at least 40 years. Fire activity is influenced by a range of other factors including land management practices. However, land management alone cannot explain recent increases in wildfire extent and intensity in the western US or southeast Australia because increased fire weather amplifies fire risk where fuels remain available.

The new analysis shows that:

  • Well over 100 studies published since 2013* show strong consensus that climate change promotes the weather conditions on which wildfires depend, enhancing their likelihood.
  • Natural variability is superimposed on the increasingly warm and dry background conditions resulting from climate change, leading to more extreme fires and more extreme fire seasons.
  • Land management can ameliorate or compound climate-driven changes in wildfire risk, either through fuel reductions or fuel accumulation as unintended byproduct of fire suppression. Fire suppression efforts are made more difficult by climate change.
  • There is an unequivocal and pervasive role of climate change in increasing the intensity and length in which fire weather occurs; land management is likely to have contributed too, but does not alone account for recent increases in wildfire extent and severity in the western US and in southeast Australia.

In an explainer for Carbon Brief on 14 July 2020 "Explainer: How climate change is affecting wildfires around the world" Daisy Dunne writes:

This year has seen unprecedented wildfires cause havoc across the world. Australia recently battled its largest bushfire on record, while parts of the Arctic, the Amazon and central Asia have also experienced unusually severe blazes.

It follows on from “the year rainforests burned” in 2019. Last year saw the Amazon face its third-largest fire on record, while intense blazes also raged in Indonesia, North America and Siberia, among other regions.

A rapid analysis released this year found that climate change made the conditions for Australia’s unprecedented 2019-20 bushfires at least 30% more likely. Further analysis – visualised below [in article] in an interactive map – has shown that, globally, climate change is driving an increase in the weather conditions that can stoke wildfires.

But despite a growing field of evidence suggesting that climate change is making the conditions for fire more likely, research finds that the total area burned by wildfires each year decreased by up to a quarter in the past two decades.

Understanding this paradox requires scientists to assess a vast range of influential factors, including climate change, human land-use and political and social motivations.

In this explainer, Carbon Brief examines how wildfires around the world are changing, the influence of global warming and how risks might multiply in the future.

continue reading article

In an article "The many ways climate change worsens California wildfires" in Yale Climate Connections on 13 Nov 2018, Dana Nuccitelli responds to President Trump’s tweets suggesting forest mismanagement is to blame for California’s wildfires:

The reality is that about 57 percent of the state’s forests are owned and managed by the federal government, and another 40 percent by families, companies, and Native American tribes. Forest management does play some role in creating wildfire fuel, but some wildfires aren’t even located in forests. Moreover, scientific evidence clearly shows that climate change is exacerbating California’s wildfires in different ways:

Higher temperatures dry out vegetation and soil, creating more wildfire fuel. Climate change is shortening the California rainy season, thus extending the fire season. Climate change is also shifting the Santa Ana winds that fan particularly dangerous wildfires in Southern California. The warming atmosphere is slowing the jet stream, leading to more California heat waves and high-pressure ridges in the Pacific. Those ridges deflect from the state some storms that would otherwise bring much-needed moisture to slow the spread of fires.

Writing about wildfires in Canada, "Did climate change contribute to the Fort McMurray fire?" Zane Schwartz wrote in MacLean's on 4 May 2016:

Experts say forest fires are more frequent, and more intense, due to climate change