Global warming is expected to alter wildfire potential and fire season severity, but the magnitude and location of change is still unclear. Here, we show that climate largely determines present fire-prone regions and their fire season. We categorize these regions according to the climatic characteristics of their fire season into four classes, within general Boreal, Temperate, Tropical and Arid climate zones. Based on climate model projections, we assess the modification of the fire-prone regions in extent and fire season length at the end of the 21st century. We find that due to global warming, the global area with frequent fire-prone conditions would increase by 29%, mostly in Boreal (+111%) and Temperate (+25%) zones, where there may also be a significant lengthening of the potential fire season. Our estimates of the global expansion of fire-prone areas highlight the large but uneven impact of a warming climate on Earth’s environment.

Plants play a key role in the hydrological cycle, yet their contribution to extreme rainfall remains uncertain. Here we show that more than half of the vast amounts of water accumulated in the recent Germany and Belgium floods were supplied by vegetation (41% from transpiration, 11% from interception loss). We found that intercontinental transport of moisture from North American forests (which contributed more than 463 billion liters of water to the event) was a more important source than evaporation over nearby seas, such as the Mediterranean or the North Sea. Our results demonstrate that summer rainfall extremes in Europe may be strongly dependent on plant behavior and suggest that significant alterations in vegetation cover, even of remote regions, could have a direct effect on these potentially catastrophic events.

The Mediterranean region has been declared a climate change hotspot due, among other reasons, to an expected increase in the torrential rains that frequently affect this densely populated area. However, the extent to which these torrential rains are connected to other regions outside the Mediterranean remains uncertain. Here we simulate 160 extreme precipitation events with an atmospheric model enabled for state-of-the-art moisture tracking and demonstrate that large scale moisture transport is a more important factor than evaporation over local sources. We find that the average precipitation fraction with source in the Mediterranean is only 35%, while 10% is from evapotranspiration over nearby land in continental Europe and 25% originates in the North Atlantic. The remaining 30% comes from several more distant source regions, sometimes as remote as the tropical Pacific or the Southern Hemisphere, indicating direct connections with multiple locations on the planet and a global scale energy redistribution. Our results point to the importance of approaching these extreme episodes from a more global rather than purely regional perspective, especially when attempting to attribute them to climate change.

<p>Due to its strong connection with meteorological conditions and vegetation structure, fire activity is affected by anthropogenic climate change. As a direct effect, climate regulates fuel moisture, so warmer and drier conditions are linked to higher fuel flammability, increasing fire risk. We use data from ERA5 and different CMIP6 models to build a database of fuel moisture (for both live and dead fuels) under real conditions (factual) and modified conditions without the influence of global warming (counterfactual). We then calculate the rate of spread of some observed wildfires in the Iberian Peninsula from 2001 to 2021, from both factual and counterfactual data. We find that climate change influence is already noticeable and significant. We also identify the areas most vulnerable to the impacts of climate change and the time of the year when these impacts are strongest. </p>

In their comment, Staal and Koren replicate our experiment using a different methodology, namely a Lagrangian moisture tracking method. Their results largely agree with ours, which is therefore a good indication of the high robustness and accuracy of these findings. Although this comparison is of great value, to a large extent their comment is a criticism of our interpretation of the results, with which we disagree. Their main objection refers to the fact that, since they show that the relative contribution of forests to the precipitation recorded during the event was not anomalous (above average), their ‘central role’ would not be justified. However, a relevant or even a dominant contribution does not necessarily have to be anomalous, so that claim does not hold. In other words, forests played a ‘central role’ because their contribution (adding transpiration and interception loss) was greater than 50%, regardless of what their average contribution to precipitation in the first half of July might be.