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El Niño 2015 continues its climb in the record books, why the Sun is not the cause of global warming, and climate tipping points we'll reach even before warming hits 2 degrees C. It's What's Up In Climate Change.
OUT OF THIS WORLD | What's Up In Climate Change

El Niño 2015 continues to strengthen. Now 'too big to fail'

Scott Sutherland
Meteorologist/Science Writer

Thursday, October 15, 2015, 1:46 PM - El Niño 2015 continues its climb in the record books, why the Sun is not the cause of global warming, and climate tipping points we'll reach even before warming hits 2 degrees C. It's What's Up In Climate Change.

El Niño 2015 "too big to fail"

El Niño is in full swing and strengthening, according to the latest update from the US National Oceanic and Atmospheric Administration (NOAA).

Sea surface temperature differences are reflected in differences in sea surface heights, as shown in the above comparison between Oct 5, 1997 and Oct 4, 2015. Credit: NASA Earth Observatory

As of September's monthly tally, water temperatures along the central part of the equatorial Pacific Ocean (called the Niño 3.4 region) have climbed even higher. Compared to all other years going back to 1950, the three-month average of July-Sept is third highest on record, at +1.5oC above normal, behind 1987 (+1.6oC) and 1997 (+1.7oC). The one-month average for September is now second only to the "super El Niño" of 1997.

Temperature departure from normal in the central equatorial Pacific Ocean (degrees C), with 2015 compared to other strong El Niño years. Credit: Climate.gov

While this graph only includes data up until September 2015, according to NASA's Earth Observatory:

"October sea level height anomalies show that 2015 is as big or bigger in heat content than 1997."

"Whether El Niño gets slightly stronger or a little weaker is not statistically significant now. This baby is too big to fail," Bill Patzert, a climatologist at NASA’s Jet Propulsion Laboratory, said in a statement. "Over North America, this winter will definitely not be normal. However, the climatic events of the past decade make ‘normal’ difficult to define."

According to NOAA's October 8th outlook, the pattern is expected to peak sometime in late fall or early winter and then slowly weaken through spring of 2016. Along with this, the best consensus of their forecasts puts El Niño 2015 as the strongest on record (at around +2.4oC above normal in the Niño 3.4 region, compared to the +2.3oC seen there in 1997).

What will this mean for winter across North America? Unless the pattern stays locked in for the rest of the winter, in which case it would probably far surpass the intensity of the 1997 El Niño, the eastern half of the continent may not get the hoped-for mild season out of it.

Why it's NOT the Sun

As the Sun supplies Earth with the vast majority of the energy that goes into our weather and climate systems, it was one of the first of the "usual suspects" that scientists examined when trying to determine the cause of the current trend in global warming.

One clue that pointed to the fact that it was NOT, in fact, the Sun causing the problem is the pattern of the warming we're seeing.

If increases in solar radiation were causing our atmosphere to warm up, we would see warming at all levels of the atmosphere. However, detailed measurements showed that it is the lowest level of the atmosphere, known as the troposphere - the layer that contains the majority of our weather and where almost all of our air pollution (carbon or otherwise) is dumped - that is warming, while layers above it (especially the stratosphere) are cooling. That points to a source from below, rather than above.

There is a more fundamental reason why the Sun isn't the culprit behind global warming, though. Dr. Judith Lean, the Senior Scientist for Sun-Earth System Research at the U.S. Naval Research Laboratory, explains below:

The pattern of solar output has been tracked for years, and is shown in the graph below:

Solar output, with the Maunder Minimum in the 1600-1700s, the Dalton Minimum in the early 1800s, and the modern maximum. Note the current downward trend since the middle of the 20th century. Credit: Dr. Greg Kopp, UC Boulder

Seeing a gradual downward trend in solar output at the same time as we record gradually rising surface temperatures around the globe, it's clear that the Sun becomes an extremely unlikely source of the problem.

Abrupt climate shifts possible at less than 2o of warming

According to new research, even if we can restrict global warming to the goal of just 2 degrees Celsius above pre-industrial levels, chances are we will still see many instances of abrupt climate shifts.

Based on a study of the climate models used in the latest IPCC report, scientists have found 37 specific cases where the models reached "climate tipping points" that resulted in sudden local changes - whether it was response in the local biosphere, changes in sea ice or land ice, or in ocean currents and circulations. Nearly half of those instances occurred while global temperatures were still below the +2oC "threshold" currently given for limiting global warming.

The tally is rather high, however the researchers note that while these abrupt climate tipping points are found in all of their model runs, exactly which tipping points showed up was much less consistent. 

"This illustrates the high uncertainty in predicting tipping points," Dr. Sybren Drijfhout, Professor of Physical Oceanography and Climate Physics at the University of Southampton, said in a statement. "More precisely, our results show that the different state-of-the-art models agree that abrupt changes are likely, but that predicting when and where they will occur remains very difficult. Also, our results show that no safe limit exists and that many abrupt shifts already occur for global warming levels much lower than two degrees."

The study, Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models, also reveals that there is a split between land and ocean. While tipping points over land were usually reached at temperatures above the +2oC limit, it was ocean tipping points that occurred more often below that goal.

The most common tipping point seen across the different models: abrupt changes in sea ice.

2015 September Arctic Sea Ice Minimum. Credit: NASA's Goddard Scientific Visualization Studio

Sources: NASA EO/Climate.gov | Yale Climate Connections | University of Southampton/PNAS

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