Recent increases in regional wildfire activity have been linked to climate change. Here, we analyse trends in observed global extreme fire weather and their meteorological drivers from 1979 to 2020 using the ERA5 reanalysis. Trends in annual extreme (95th percentile) values of the fire weather index (FWI95), initial spread index (ISI95) and vapour pressure deficit (VPD95) varied regionally, with global increases in mean values of 14, 12 and 12%, respectively. Significant increases occurred over a quarter to almost half of the global burnable land mass. Decreasing relative humidity was a driver of over three-quarters of significant increases in FWI95 and ISI95, while increasing temperature was a driver for 40% of significant trends. Trends in VPD95 were predominantly associated with increasing temperature. These trends are likely to continue, as climate change projections suggest global decreases in relative humidity and increases in temperature that may increase future fire risk where fuels remain abundant.
This is a preview of subscription content, access via your institution
Open Access articles citing this article.
Communications Earth & Environment Open Access 05 September 2023
Fire Ecology Open Access 14 June 2023
Nature Communications Open Access 30 March 2023
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 print issues and online access
$209.00 per year
only $17.42 per issue
Rent or buy this article
Prices vary by article type
Prices may be subject to local taxes which are calculated during checkout
The hourly ERA5 data used for this study are available at https://doi.org/10.24381/cds.adbb2d47. The fire weather metrics derived for the period 1979–2020 that support the findings of this study are available from https://doi.org/10.5281/zenodo.5567021 (daily ISI and FWI) and https://doi.org/10.5281/zenodo.5567062 (daily maximum VPD). Global mean land-surface temperatures are available from the NOAA National Centers for Environmental information, Climate at a Glance: Global Time Series (published July 2021), at https://www.ncdc.noaa.gov/cag/. The global biomes used in this study are available at https://www.worldwildlife.org/publications/terrestrial-ecoregions-of-the-world and land-cover data are available at https://doi.org/10.5067/MODIS/MCD12Q1.006.
Abatzoglou, J. T., Williams, A. P., Boschetti, L., Zubkova, M. & Kolden, C. A. Global patterns of interannual climate-fire relationships (2018). Glob. Change Biol. 24, 5164–5175 (2018).
Littell, J. S., McKenzie, D., Peterson, D. L. & Westerling, A. L. Climate and wildfire area burned in western US ecoprovinces, 1916-2003. Ecol. Appl. 19, 1003–1021 (2009).
Abatzoglou, J. T. & Kolden, C. A. Relationships between climate and macroscale area burned in the western United States. Int. J. Wildland Fire 22, 1003–1020 (2013).
Wang, X. et al. Projected changes in daily fire spread across Canada over the next century. Environ. Res. Lett. 12, 025005 (2017).
Hanes, C. C. et al. Fire-regime changes in Canada over the last half century. Can. J. Res. 49, 256–269 (2019).
Amiro, B. D. et al. Fire weather index system components of large fires in the Canadian boreal forest. Int. J. Wildland Fire 13, 391–400 (2004).
Flannigan, M. D., Krawchuck, M. A., de Groot, W. J., Wotton, B. M. & Gowman, L. M. Implications of changing climate for global wildland fire. Int. J. Wildland Fire 18, 483–507 (2009).
Bowman, D. M. J. S. et al. Human exposure and sensitivity to globally extreme wildfire events. Nat. Ecol. Evol. 1, 0058 (2017).
Coogan, S. C. P., Robinne, F.-N., Jain, P. & Flannigan, M. D. Scientists’ warning on wildfire—a Canadian perspective. Can. J. Res. 49, 1015–1023 (2019).
Abatzoglou, J. T., Williams, A. P. & Barbero, R. Global emergence of anthropogenic climate change in fire weather indices. Geophys. Res. Lett. 46, 326–336 (2019).
Van Wagner, C. E. et al. Development and Structure of the Canadian Forest Fire Weather Index System (Canadian Forestry Service Headquarters, 1987); https://www.eea.europa.eu/data-and-maps/indicators/forest-fire-danger-3/camia-et-al.-2008-past
Flannigan, M. D. & Harrington, J. B. A study of the relation of meteorological variables to monthly provincial area burned by wildfire in Canada (1953-80). J. Appl. Meteorol. 27, 441–452 (1988).
Flannigan, M. D. et al. Fuel moisture sensitivity to temperature and precipitation: climate change implications. Clim. Change 134, 59–71 (2016).
Jolly, W. M. et al. Climate-induced variations in global wildfire danger from 1979 to 2013. Nat. Commun. 6, 7537 (2015).
Touma, D., Stevenson, S., Lehner, F. & Coats, S. Human-driven greenhouse gas and aerosol emissions cause distinct regional impacts on extreme fire weather. Nat. Commun. 12, 212 (2021).
Clarke, H. G., Smith, P. L. & Pitman, A. J. Regional signatures of future fire weather over eastern Australia from global climate models. Int. J. Wildland Fire 20, 550–562 (2011).
Bedia, J. et al. Sensitivity of fire weather index to different reanalysis products in the Iberian Peninsula. Nat. Hazards Earth Syst. Sci. 12, 699–708 (2012).
Jain, P., Wang, X. & Flannigan, M. D. Trend analysis of fire season length and extreme fire weather in North America between 1979 and 2015. Int. J. Wildland Fire 26, 1009–1020 (2017).
Dowdy, A. J. Climatological variability of fire weather in Australia. J. Appl. Meteorol. Climatol. 57, 221–234 (2018).
Zhao, F., Liu, Y. & Shu, L. Change in the fire season pattern from bimodal to unimodal under climate change: the case of Daxing’anling in Northeast China. Agric. Meteorol. 291, 108075 (2020).
Hersbach, H. et al. The ERA5 global reanalysis. Q. J. R. Meteorol. Soc. 146, 1999–2049 (2020).
Abatzoglou, J. T. & Williams, A. P. Impact of anthropogenic climate change on wildfire across western US forests. Proc. Natl Acad. Sci. USA 113, 11770–11775 (2016).
Kirchmeier-Young, M. C., Gillet, N. P., Zwiers, F. W., Cannon, A. J. & Anslow, F. S. Attribution of the influence of human-induced climate change on an extreme fire season. Earths Future 7, 2–10 (2019).
Pausas, J. G. & Ribeiro, E. The global-fire productivity relationship. Glob. Ecol. Biogeogr. 22, 728–736 (2013).
Cochrane, M. A. Fire science for rainforests. Nature 421, 913–919 (2003).
Ziel, R. H. et al. A comparison of fire weather indices with MODIS fire days for the natural regions of Alaska. Forests 11, 516 (2020).
Giannaros, T. M., Kotroni, V. & Lagouvardos, K. Climatology and trend analysis (1987–2016) of fire weather in the Euro-Mediterranean. Int. J. Climatol. 41, E491–E508 (2021).
Harris, S. & Lucas, C. Understanding the variability of Australian fire weather between 1973 and 2017. PLoS ONE 14, e0222328 (2019).
Climate at a Glance (NOAA, 2021); https://www.ncdc.noaa.gov/cag/
van Oldenborgh, G. J. et al. Attribution of the Australian bushfire risk to anthropogenic climate change. Nat. Hazards Earth Syst. Sci. 21, 941–960 (2021).
Barbero, R., Abatzoglou, J. T., Pimont, F., Ruffault, J. & Curt, T. Attributing increases in fire weather to anthropogenic climate change over France. Front. Earth Sci. https://doi.org/10.3389/feart.2020.00104 (2020).
Byrne, M. P. & O’Gorman, P. A. Understanding decreases in land relative humidity with global warming: conceptual model and GCM simulations. J. Clim. 29, 9045–9061 (2016).
Willett, K. M., Jones, P. D., Gillett, N. P. & Thorne, P. W. Recent changes in surface humidity: development of the HadCRUH dataset. J. Clim. 21, 5364–5383 (2008).
Matsoukas, C. et al. Potential evaporation trends over land between 1983-2008: driven by radiative fluxes or vapour-pressure deficit? Atmos. Chem. Phys. 11, 7601–7616 (2011).
Grotjahn, R. & Huynh, J. Contiguous US summer maximum temperature and heat stress trends in CRU and NOAA climate division data plus comparisons to reanalyses. Sci. Rep. 8, 11146 (2018).
Denson, E., Wasko, C. & Peel, M. C. Decreases in relative humidity across Australia. Environ. Res. Lett. https://doi.org/10.1088/1748-9326/ac0aca (2021).
Barkhordarian, A., Saatchi, S. S., Behrangi, A., Loikith, P. C. & Mechoso, C. R. A recent systematic increase in vapor pressure deficit over tropical South America. Sci. Rep. 9, 15331 (2019).
Findell, K. L. et al. The impact of anthropogenic land use and land cover change on regional climate extremes. Nat. Commun. 8, 989 (2017).
McKinnon, K. A., Poppick, A. & Simpson, I. R. Hot extremes have become drier in the United States Southwest. Nat. Clim. Change https://doi.org/10.1038/s41558-021-01076-9 (2021).
Berg, A. et al. Land–atmosphere feedbacks amplify aridity increase over land under global warming. Nat. Clim. Change 6, 869–874 (2016).
Mishra, V. et al. Moist heat stress extremes in India enhanced by irrigation. Nat. Geosci. 13, 722–728 (2020).
Dong, B. & Dai, A. The influence of the interdecadal Pacific oscillation on temperature and precipitation over the globe. Clim. Dyn. 45, 2667–2681 (2015).
Fischer, E. M. & Knutti, R. Robust projections of combined humidity and temperature extremes. Nat. Clim. Change 3, 126–130 (2013).
Tymstra C., Flannigan M. D., Stocks B. J., Cai X. & Morrison K. Wildfire management in Canada: review, challenges and opportunities. Prog. Disaster Sci. https://doi.org/10.1016/j.pdisas.2019.100045 (2020).
Flannigan, M. D., Stocks, B., Turetsky, M. & Wotton, M. Impacts of climate change on fire activity and fire management in the circumboreal forest. Glob. Change Biol. 15, 549–560 (2009).
Chen, Y. et al. Future increases in Arctic lightning and fire risk for permafrost carbon. Nat. Clim. Change https://doi.org/10.1038/s41558-021-01011-y (2021).
Hope, E. S., McKenney, D. W., Pedlar, J. H., Stocks, B. J. & Gauthier, S. Wildfire suppression costs for Canada under a changing climate. PLoS ONE 11, e0157425 (2016).
Podur, J. & Wotton, B. M. Will climate change overwhelm fire management capacity? Ecol. Modell. 221, 1301–1309 (2010).
Abatzoglou, J. T., Juang, C. S., Williams, A. P., Kolden, C. A. & Westerling, A. L. Increasing synchronous fire danger in forests of the western United States. Geophys. Res. Lett. 48, e2020GL091377 (2021).
Olson, D. M. et al. Terrestrial ecoregions of the world: a new map of life on Earth. Bioscience 51, 933–938 (2001).
Copernicus Climate Change Service Data Store (Copernicus Climate Change Service, accessed 4 March 2020); https://confluence.ecmwf.int/display/CKB/ERA5%3A+data+documentation
Ramon, J., Lledo, L., Torralba, V., Soret, A. & Doblas-Reyes, F. J. What global reanalysis best represents near-surface winds? Q. J. R. Meteorol. Soc. 145, 3236–3251 (2019).
Beck, H. E. et al. Daily evaluation of 26 precipitation datasets using stage-IV gauge-radar data for the CONUS. Hydrol. Earth Syst. Sci. 23, 207–224 (2019).
Tarek, M., Brissette, F. P. & Arsenault, R. Evaluation of the ERA5 reanalysis as a potential reference dataset for hydrological modelling over North America. Hydrol. Earth Syst. Sci. 24, 2527–2544 (2020).
Torralba, V., Doblas-Reyes, F. J. & Gonzalez-Reviriego, N. Uncertainty in recent near-surface wind speed trends: a global reanalysis intercomparison. Environ. Res. Lett. 12, 114019 (2017).
Dinerstein, E. et al. An ecoregion-based approach to protecting half the terrestrial realm. BioScience 67, 534–545 (2017).
Andela, N. et al. The global fire atlas of individual fire size, duration, speed and direction. Earth Syst. Sci. Data 11, 529–552 (2019).
Wotton, B. M. Interpreting and using outputs from the Canadian Forest Fire Danger Rating System in research applications. Environ. Ecol. Stat. 16, 107–131 (2009).
Field, R. D. et al. Development of a global fire weather database. Nat. Hazards Earth Syst. Sci. 15, 1407–1423 (2015).
Bedia, J. et al. Global patterns in the sensitivity of burned area to fire weather: implications for climate change. Agric. Meteorol. 214–215, 369–379 (2015).
McElhinny, M., Beckers, J. F., Hanes, C., Flannigan, M. & Jain, P. A high-resolution reanalysis of global fire weather from 1979 to 2018 – overwintering the Drought Code. Earth Syst. Sci. Data 12, 1823–1833 (2020).
Wotton, B. M. & Flannigan, M. D. Length of the fire season in a changing climate. Forestry Chron. 69, 187–192 (1993).
Sedano, F. & Randerson, J. T. Vapor pressure deficit controls on fire ignition and fire spread in boreal forest ecosystems. Biogeosciences 11, 1309–1353 (2014).
Williams, P. A. et al. Correlations between components of the water balance and burned area reveal new insights for predicting forest fire area in the southwest United States. Int. J. Wildland Fire 24, 14–26 (2014).
Williams, A. P. et al. Observed impacts of anthropogenic climate change on wildfire in California. Earths Future 7, 892–910 (2019).
Mueller, S. E. et al. Climate relationships with increasing wildfire in the southwestern US from 1984 to 2015. For. Ecol. Manage. 460, 117861 (2020).
Alduchov, O. A. & Eskridge, R. E. Improved Magnus form approximation of saturation vapor pressure. J. Appl. Meteorol. 35, 601–609 (1996).
Knauer, J., El-Madany, T. S., Zaehle, S. & Migliavacca, M. Bigleaf—an R package for the calculation of physical and physiological ecosystem properties from eddy covariance data. PLoS ONE 13, e0201114 (2018).
Friedl, M. A. et al. MODIS Collection 5 global land cover: algorithm refinements and characterization of new datasets. Remote Sens. Environ. 114, 168–182 (2010).
Loveland, T. R. & Belward, A. S. The IGBP-DIS global 1 km land cover data set, DISCover: first results. Int. J. Remote Sens. 18, 3291–3295 (1997).
Mann, H. B. Nonparametric tests against trend. Econometrica 13, 245–259 (1945).
Kendall, M. G. Rank Correlation Methods (Griffin, 1975).
Theil, H. A rank-invariant method of linear and polynomial regression analysis. I, II, III. Nederl. Akad. Wetensch. Proc. 53, part I: 386–392; part II: 521–525; part III: 1397–1412 (1950).
Sen, P. K. Estimates of the regression coefficient based on Kendall’s tau. J. Am. Stat. Assoc. 63, 1379–1389 (1968).
Yue, S., Pilon, P. & Phinney, B. Canadian streamflow trend detection: impacts of serial and cross-correlation. Hydrol. Sci. J. 48, 51–63 (2003).
Wilks, D. S. On ‘field significance’ and the false discovery rate. J. Appl. Meteorol. Climatol. 45, 1181–1189 (2006).
Wilks, D. ‘The stippling shows statistically significant grid points’: how research results are routinely overstated and overinterpreted, and what to do about it. Bull. Am. Meteorol. Soc. 97, 2263–2273 (2016).
Libiseller, C. & Grimvall, A. Performance of partial Mann–Kendall tests for trend detection in the presence of covariates. Environmetrics 13, 71–84 (2002).
Mediero, L., Santillán, D., Garrote, L. & Granados, A. Detection and attribution of trends in magnitude, frequency and timing of floods in Spain. J. Hydrol. 517, 1072–1088 (2014).
Dowdy, A. J., Mills, G. A., Finkele, K. & de Groot, W. Index sensitivity analysis applied to the Canadian Forest Fire Weather Index and the McArthur Forest Fire Danger Index. Meteorol. Appl. 17, 298–312 (2010).
Millard, S. P. EnvStats: An R Package for Environmental Statistics (Springer, 2013).
Pohlert, T. trend: Non-Parametric Trend Tests and Change-Point Detection. R package v.1.1.4. https://CRAN.R-project.org/package=trend (2020).
We thank the Canadian Partnership for Wildland Fire Science for their support. P.J. thanks M. McElhinny and J. Beckers for their help in developing code for FWI calculation. J.T.A. was partially supported by NSF award no. OAI-2019762.
The authors declare no competing interests.
Peer review information Nature Climate Change thanks Ubirajara Oliveira and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Jain, P., Castellanos-Acuna, D., Coogan, S.C.P. et al. Observed increases in extreme fire weather driven by atmospheric humidity and temperature. Nat. Clim. Chang. 12, 63–70 (2022). https://doi.org/10.1038/s41558-021-01224-1
This article is cited by
Fire Ecology (2023)
Fuel treatment effectiveness at the landscape scale: a systematic review of simulation studies comparing treatment scenarios in North America
Fire Ecology (2023)
Communications Earth & Environment (2023)
Nature Water (2023)
Nature Communications (2023)