According to the UN 2020 is set to rank among hottest years on record despite ‘La Nina’ cooling and could also be contributing to an unusually active hurricane season.
Global temperatures boosted by climate change will still be higher than usual despite the cooling effect of a “moderate to strong” La Nina weather phenomenon, the UN said Thursday.
The World Meteorological Organization (WMO) said La Nina “has developed and is expected to last into next year, affecting temperatures, precipitation and storm patterns in many parts of the world.”
La Nina is considered the stormy sister of El Nino, which occurs every two to seven years when the prevailing trade winds that circulate surface water in the tropical Pacific start to weaken.
El Nino, which has a major influence on weather and climate patterns and associated hazards such as heavy rains, floods and drought, has a warming influence on global temperatures, whilst La Nina tends to have the opposite effect.
All naturally occurring climate events now take place against a background of human-induced climate change which is exacerbating extreme weather and affecting the water cycle.
La Nina typically has a cooling effect on global temperatures, but this is more than offset by the heat trapped in our atmosphere by greenhouse gases.
Therefore, 2020 remains on track to be one of the warmest years on record and 2016-2020 is expected to be the warmest five-year period on record.
La Nina years now are warmer even than years with strong El Nino events of the past.
The UN agency pointed to fresh data indicating that this year’s La Nina would among other things lead to below normal rainfall in the Horn of Africa region and Central Asia, while Southeast Asia, some Pacific islands and the northern part of South America would see more rain than usual.
There is a connection between La Nina and El Nino and hurricane frequency. El Nino tends to suppress frequency and La Nina tends to encourage them, so if we do have a strong hurricane season, La Nina could be contributing to that.
The latest Hurricane Zeta barrelled through the southern United States and is the 27th storm of the season.
In September, meteorologists were forced to use the Greek alphabet to name Atlantic storms for only the second time ever, after the 2020 hurricane season blew through their usual list, ending on Tropical Storm Wilfred.
Zeta was expected to be the last hurricane of the season, which typically runs from June through October, although the warming of the oceans, which provides more energy for hurricanes, has allowed storms to rage later into the year.
La Nina was instead expected to create drier than normal conditions in the southern United States and northern Mexico over the next three months. So it may go from hurricanes and flooding to dry conditions fairly quickly.
AFP / Crickey Conservation Society 2020.