Why in news? New York City’s air quality was recently among the worst in the world due to smoke drifting from the wildfires in Canada.

Highlights:

• Areas from the mid-Atlantic through the northeast and upper parts of the Great Lakes registered air quality in ‘unhealthy’ or worse categories.
• Quebec is Canada’s largest province by area is the most currently active wildfires.

What’s causing the wildfires?

• Lightning is the main precursor of natural wildfires.
• Lightning electric currents that flow for more than some tens of milliseconds, called long-continuing currents (LCC), are likely to produce fires.
• There increased activity over land, implying a higher risk of lightning-ignited wildfires in the future.

How does lightning work?

• During a storm, water droplets in warmer air and ice crystals that condensed in cooler air coalesce together to form thunderstorm clouds (usually cumulonimbus clouds).
• Contact between these droplets and crystals produces a static electrical charge in the clouds, negative and positive charges in the clouds build up.
• Over time, the voltage difference becomes high enough to surmount the resistance presented by the air, leading to a rapid discharge of electric charge resulting lightning flash.
• It can occur between oppositely charged surfaces within a thunderstorm cloud or between such surfaces in the cloud and on the ground.

Is lightning a climate indicator?

• Long-term changes in lightning patterns reflect, at least in part, changes wrought by the climate crisis.
• The World Meteorological Organisation recognises lightning to be an essential climate variable that contributes critically to the way the earth’s climate is characterised.
• Lightning also produces nitrogen oxides, which react with oxygen in the air to form ozone, which is a strong greenhouse gas.