NOAA’s National Weather Service Climate Prediction Center released its monthly El Niño/Southern oscillation (ENSO) Diagnostic Discussion:
Synopsis: El Niño is expected to strengthen and last through the Northern Hemisphere Winter 2009-2010.
A weak El Niño was present during July 2009, as monthly sea surface temperatures (SST) departures ranged from +0.5°C to +1.5°C across the equatorial Pacific Ocean, with the largest anomalies in the eastern half of the basin. Consistent with this warmth, all of the Niño-region SST indices were between +0.6°C to +1.0°C throughout the month. Subsurface oceanic heat content (average temperatures in the upper 300m of the ocean) anomalies continued to reflect a deep layer of anomalous warmth between the ocean surface and thermocline.
A majority of the model forecasts for the Niño-3.4 SST index [Fig. 6, at the bottom] suggest El Niño will continue to strengthen. While there is disagreement on the eventual strength of El Niño, nearly all of the dynamical models predict a moderate-to-strong El Niño during the Northern Hemisphere Winter 2009-10.
This announcement is not surprising news – it mainly means the ENSO models are on track (see NOAA says “El Niño arrives; Expected to Persist through Winter 2009-10″ – and that means record temperatures are coming and this will be the hottest decade on record).
But this evolving story remains a big deal from the perspective of heating up global temperatures and cooling off denier talking points. After all, the La Niña conditions over the past 18 months helped temporarily mute the strong human-caused warming signal, allowing the global warming deniers to push their nonsensical global cooling meme with the help of the status quo media (see “Media enable denier spin 1: A (sort of) cold January  doesn’t mean climate stopped warming“).
Remember, back in January, NASA had predicted: “Given our expectation of the next El Niño beginning in 2009 or 2010, it still seems likely that a new global temperature record will be set within the next 1-2 years, despite the moderate negative effect of the reduced solar irradiance.“
So I will continue posting at least monthly updates. Regular readers can skip the rest of this post (though it does have some new figues).
It is the warming in the Nino 3.4 region of the Pacific that is typically used to define an El Niño. The region can be seen in this figure:
How are El Niño and La Niña defined?
El Niño and La Niña are officially defined as sustained sea surface temperature anomalies of magnitude greater than 0.5°C across the central tropical Pacific Ocean. When the condition is met for a period of less than five months, it is classified as El Niño or La Niña conditions; if the anomaly persists for five months or longer, it is called an El Niño or La Niña “episode.”
As the planet warms decade by decade thanks to human emissions of greenhouse gases, global temperature records tend to be set in El Niño years, like 1998, 2005 and 2007, whereas sustained La Niñas tend to cause relatively cooler years.
Human-caused global warming is so strong, however, that as NASA explained, it took a serious La Niña, plus unusually sustained low levels of solar irradiance, to make 2008 as cool as it was. Yet, notwithstanding the global warming deniers and the status quo media, 2008 wasn’t actually cool. Indeed, 2008 was almost 0.1°C warmer than the decade of the 1990s averaged as a whole. And not that there was any realistic chance global temperatures would collapse this year, but now it is quite safe to say that “this will be the hottest decade in recorded history by far.” The 2000s are on track to be nearly 0.2°C warmer than the 1990s. And that temperature jump is especially worrisome since the 1990s were only 0.14°C warmer than the 1980s.
If we have a moderate to strong El Niño, then, as NASA says, record global temperatures are all but inevitable. The NCDC already reported June was the second hottest on record with ocean temperatures the warmest on record — a full 0.11°F warmer than the 2005 record. It typically takes several months for ENSO to impact global temps.
And this brings us back to NOAA’s updated prediction. Here were the model forecasts from June:
Figure 5. Forecasts of sea surface temperature (SST) anomalies for the Niño 3.4 region (5°N-5°S, 120°W-170°W). Figure courtesy of the International Research Institute (IRI) for Climate and Society. Figure updated 15 June 2009.
Now here is the update as of July 16 [don’t ask me why these are always 3 weeks old, ask NOAA]:
Note that the June models that predicted a strengthening were correct. Also, Niño 3.4 in July averaged more than +0.8°C, so again, we see the July models that had predicted strengthening seem to be more accurate.
A hot summer and fall — how timely would that be for debating a climate bill?