PLEA Network

14 September 2023, The Conversation: How rising water vapour in the atmosphere is amplifying warming and making extreme weather worse. This year’s string of record-breaking disasters – from deadly wildfires and catastrophic floods to record-high ocean temperatures and record-low sea ice in Antarctica – seems like an acceleration of human-induced climate change. And it is. But not only because greenhouse gas emissions continue to rise. What we are also observing is the long-predicted water vapour feedback within the climate system. Since the late 1800s, global average surface temperatures have increased by about 1.1°C, driven by human activities, most notably the burning of fossil fuels which adds greenhouse gases (carbon dioxide and methane) to the atmosphere. As the atmosphere warms, it can hold more moisture in the form of water vapour, which is also a greenhouse gas. This in turn amplifies the warming caused by our emissions of other greenhouse gases. Some people mistakenly believe water vapour is a driver of Earth’s current warming. But as I explain below, water vapour is part of Earth’s hydrological cycle and plays an important role in the natural greenhouse effect. Its rise is a consequence of the atmospheric warming caused by our emissions arising especially from burning fossil fuels. Water vapour: the other greenhouse gas. For every degree Celsius in warming, the water-holding capacity of the atmosphere increases by about 7%. Record-high sea temperatures ensure there is more moisture (in the form of water vapour) in the atmosphere, by an estimated 5-15% compared to before the 1970s, when global temperature rise began in earnest. Read more here