More wildfires have burned around the Russian capital this year than in the last decade and a half, according to sensors aboard ESA’s observation satellites. The forest and peat bog fires ignited this summer amid an unprecedented heat wave of up to 40ºC.

Working like thermometers in the sky, the Along Track Scanning Radiometer and the Advanced Along Track Scanning Radiometer on ESA’s ERS-2 and Envisat satellites measure thermal-infrared radiation to take the temperature of Earth’s land surface.

Flames reach temperatures that are detected by these sensors and confirm the presence of fire.

Data gathered from fires across Russia from July 1996 to the present were used to plot the number of fires occurring monthly. The region near Moscow showed around six times the number of fires this August compared to previous years.