Europe has been warming twice as fast as the global average since the 1980s, making the region more vulnerable to wildfires.

Thousands of firefighters backed by the military and water-bombing aircraft on Monday battled dozens of wildfires across Spain and Portugal, as the death toll increased to six since the outbreaks began.

The fires in Spain this year have burned 158,000 hectares or 610 square miles, according to the European Union’s European Forest Fire Information System. That is an area roughly as big as metropolitan London.