Humidity – the second pillar of climate change
Climate change isn’t just affecting global temperature, it’s also changing the amount of water vapour in the atmosphere with potentially significant impacts, finds a new study looking at global humidity.
Kate Willett is a Met Office scientist and author of a new study looking at global humidity – the amount of water vapour held in the atmosphere as a gas.
She yesterday said:
“Think of climate change and people immediately think of rising temperatures. This isn’t wrong, but it misses a key fact that climate change is also causing shifts in humidity.
“Humidity governs the increasing likelihood of heavier rainfall and more dangerous heatwaves. We need to monitor and understand changes in surface humidity, just like temperature. Working together humidity and temperature can be thought of as the twin pillars of climate change.”
The study – published yesterday in the journal Earth System Science Data – highlighted an interesting paradox: although the amount of water vapour in the atmosphere has increased – as expected – it hasn’t increased by as much as it could have done. Kate Willett explained: “Specific humidity, the amount of water vapour in the air, has increased – this is consistent with theoretical expectation for a warming world – the air has warmed so it can and does hold more water vapour.
“However, at the same time, the air over land has become less saturated – the relative humidity is decreasing – consistent with land warming faster than ocean, where most evaporation happens.
“Our study shows that specific humidity has also increased over the oceans – this is expected because the oceans and air above have warmed so more water can be evaporated and held as a gas in the air.”
In heavy rainfall events, all of the water available tends to rain out – so more water vapour over land and ocean means heavier heavy rainfall events, increasing the likelihood of flooding – we are already seeing that this is happening.
Heat waves are becoming more frequent and more intense both in terms of temperature and humidity. This makes it harder, and even dangerous to be physically active in such conditions.
The Met Office worked in collaboration with the National Oceanography Centre to produce new climate monitoring dataset for surface humidity over oceans. The dataset is called HadISDH.marine which stands for the Met Office Hadley Centre Integrated Surface Dataset of Humidity for the marine atmosphere. It is designed to be used alongside the existing HadISDH.land to provide a global monitoring capability for studying large scale trends and variability, assessing the validity of climate models and understanding climate change.
Latest News from
Tropical Deforestation – a log jam on the road to Net Zero?16/11/2020 12:15:00
With one year to go until COP26 in Glasgow, and the launch of Together For Our Planet, Met Office Chief Scientist Professor Stephen Belcher reviews the influence tropical deforestation is having on the journey to a resilient Net Zero through the significant role they play in balancing atmospheric CO2 concentrations, storing carbon and changing the water cycle.
UK sees fifth wettest October since 186204/11/2020 15:15:15
One thing for certain is that October 2020 will be remembered for being exceptionally wet for some areas of the UK.
A wet and windy weekend ahead29/10/2020 14:43:00
With Atlantic low-pressure continuing to influence the UK weather forecast we can expect the rest of this week and upcoming weekend to remain unsettled, with heavy rain and strengthening winds.
State of the African Climate update and the importance of climate services28/10/2020 15:15:15
Every year the World Metrological Organization (WMO) publishes a range of reports examining the latest evidence on different meteorological and climatological factors.
Unsettled end to October27/10/2020 10:15:00
With the Atlantic continuing to dominate the UK weather forecast, we can expect the rest of the month to remain unsettled with heavy rain and strong winds, interspersed with brighter periods.
Future weather extremes likely to break new records22/10/2020 13:15:00
Increasingly extreme weather is one of the most damaging and costly impacts from climate change.
Rainfall on UK’s wettest day on record could have more than filled Loch Ness19/10/2020 15:15:15
Saturday 3 October 2020 is now the wettest day on record since 1891 for UK-wide rainfall. It received the greatest rainfall in any single day averaged out across the UK, beating the previous record on the 25 August 1986.
Storm Barbara to bring wind and rain to Europe19/10/2020 14:48:00
This week will see a change from the mostly dry, cloudy, chilly weather to increasing wind and rain for many and an upturn in temperatures, particularly in the south early in the week.