The record breaking heat we experienced in July 2015 is being attributed to a building El Niño event. In August the ocean surface temperatures in the equatorial Pacific were already 3 degrees Celsius above the long term average temperatures.
Although El Niño is already pronounced it is strongest between December and February. NOAA and many others project that the current El Niño will keep growing stronger and become one of the biggest on record. This means that the warming effect of El Niño will peak in the winter and last into the spring of 2016. What some are describing as the strongest El Niño in a half century will likely make 2015 the warmest year in recorded history.
Every five years or so a shift in the wind causes warmer sea surface temperatures in the equatorial Pacific. Cooler ocean surface temperatures equatorial Pacific are called La Niña while the warmer El Niño Southern Oscillation is abbreviated as ENSO. These ocean temperatures in the central and eastern equatorial Pacific have a ripple effect on global weather patterns.
Historically we know that strong El Niño effects drive up temperatures. One of the hottest months of July and hottest years on record occurred in 1998 (the fourth warmest year on record). This is also a year that had an extremely strong El Niño. Similarly we saw a strong El Niño effect in 2010 which was the second warmest year on record.
El Niño events have a wide range of adverse climate impacts from drought to floods. They tend to increase the incidence of droughts in Australia, Indonesia, the Philippines, South Africa and Northeast Brazil. While the same El Niño events tend to produce flooding in southern California, the southern US, East equatorial Africa, western South America, and southeastern South America. They also increase the number of Pacific typhoons while reducing the number of Atlantic hurricanes.
El Niño events are associated with significant damage to infrastructure. In California alone an El Niño event in the late 90s cost $500 million.
Research reveals that El Niño and climate change influence one another. El Niño warms the world, but studies reveal that a warmer world also increases the likelihood of El Niño events. Heat is absorbed by the oceans so it should come as no surprise that there is a link between climate change and El Niño events.
We can expect rising temperatures to almost double the frequency of extreme El Niño events. A 2014 study published in Nature, titled, Increasing frequency of extreme El Niño events due to greenhouse warming, outlined the relationship between El Niño events and climate change.
The finding in the 2014 study was corroborated by a recent review of the scientific evidence on ENSO and climate change. The more recent study is titled "ENSO and greenhouse warming," and it concluded that El Niño events are expected to occur more frequently as the climate warms.
This means that failure to curtail greenhouse gas emissions will cause the earth to continue warming resulting in a doubling of extreme El Niño events. As explained by the studies author's, "ENSO-related catastrophic weather events are thus likely to occur more frequently with unabated greenhouse-gas emissions." More El Niño events will also increase the likelihood of more extreme La Niña events which cause dry winters in places like California and much of the western US.
"Each kind of extreme event will occur more often," lead researcher Wenju Cai, said in a Skype interview. "A huge La Niña would tend to cause big droughts in the southwest US, but El Niño will give you floods."
Researchers based their projections on "business as usual" with regard to climate change causing greenhouse gas emissions. However, if world governments take strong action on climate change, Cai suggests that extreme El Niños could be limited to about 30 percent.
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