2017 set to be hottest non-El Nino year: UN
The year 2017 is set to be the hottest on record without a natural El Niño event that releases heat from the Pacific Ocean once every five years.
While the global average surface temperature won’t match what we saw in 2016, it is now very likely that it will be one of the three warmest years on record, according to a statement issued by the World Meteorological Organization.
Average temperatures from 2013 through 2017 are also likely to be the highest since accurate measuring began more than a century ago, constituting strong evidence of a long-term trend.
- These findings underline the rising risks to life on Earth if we fail to get on track with the aims of the Paris Agreement,” the UN added.
- Concentrations in the atmosphere of the major greenhouse gases that drive global warming continued to increase, with carbon dioxide (CO2) at 403.3 parts per million (ppm), the highest level in at least 800,000 years.
- The second-most polluting greenhouse gas — methane (CH4) — has also shot up over the past decade, driven by leakage from the gas industry’s fracking boom, and growth in global livestock.
- Compared to 1750 levels, current concentrations of CO2 and CH4 are 1.5 and 2.5 times higher, respectively.
- Earth’s frozen zones continued to contract, especially in the Arctic, where sea ice cover could disappear in summer by as early as 2030.
What are El Niño and La Niña?
El Niño and La Niña are complex weather patterns resulting from variations in ocean temperatures in the Equatorial Pacific.
El Niño and La Niña are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle. The ENSO cycle is a scientific term that describes the fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific (approximately between the International Date Line and 120 degrees West).
El Niño (Warm Phase)
The warm phase of the ENSO cycle features warmer than normal SSTs across the central and eastern equatorial Pacific
- Weaker low-level atmospheric winds along the equator
- Enhanced convection across the entire equatorial Pacific
- Effects are strongest during northern hemisphere winter due to the fact that ocean temperatures worldwide are at their warmest. This increased ocean warmth enhances convection, which then alters the jet stream such that it becomes more active over parts of the U.S. during El Niño winters. This results in enhanced precipitation across the southern U.S., including NC
- In the southeast, winter temperatures are often cooler than normal
- During hurricane season (June to November), the jet stream is aligned in such a way that the vertical wind shear is increased over the Caribbean and Atlantic. The increased wind shear helps to prevent tropical disturbances from developing into hurricanes
La Niña (Cool Phase)
This phase of the ENSO cycle features cooler than normal SSTs across the central and eastern equatorial Pacific along with:
- Stronger low-level atmospheric winds along the equator
- Decreased convection across the entire equatorial Pacific results in a more suppressed southern jet stream. Consequently, the southern U.S., including NC, sees less precipitation
- In the U.S., winter temperatures are often warmer than normal in the southeast, and cooler than normal in the Northwest
- During hurricane season (June to November), upper level winds are much lighter, and therefore more favorable for hurricane development in the Caribbean and Atlantic