Komt de hiatus terug?

De opwarmings’pauze’ of hiatus (zoals deze in het klimatologisch jargon wordt genoemd) stelt de mainstream van de klimatologische wetenschap nog steeds voor een raadsel. Extreme protagonisten van de menselijke broeikashypothese (AGW = ‘Anthropogenic Global Warming’) hebben soms de neiging de hiatus te ontkennen. Zij zien in de recente temperatuurpiek een bevestiging van hun gelijk. Maar de mainstream (en de klimaatsceptici) schrijven deze toch toe aan een kortstondig verschijnsel dat niets met CO2 heeft te maken, maar met een natuurlijke oorzaak: El Niño.

Hoe ziet de mainstream het toekomstig temperatuurverloop. Is er een kans dat de hiatus zal terugkeren en nog langer zal duren?

Ik roep in herinnering dat mainstream klimatologen als Latif en Keenlyside in 2008 reeds hebben gewezen op de mogelijkheid van een verminderde opwarming gedurende een langere periode. (Zie hier en hier.)

Maar wat denken de belangrijkste meteorologische instituten nú van het toekomstig temperatuurverloop?

Onder de titel, ‘Study: Global Warming ‘Slowdown’ Could Last Another 15 Years’, rapporteert Michael Bastasch voor de ‘Daily Caller’ daarover het volgende:

With 2016 on track to being the warmest year on record, some climate scientists and environmentalists declared the recent slowdown in global warming to be over.

But that might not be the case, according to a new study by National Oceanic and Atmospheric Administration (NOAA) scientists. They say there’s a 16 percent chance global warming could progress at a slower rate through 2020, and a 6 percent chance the slowdown could last until 2030.

“The spike in global temperatures from the 2015/2016 El Nino has caused some to declare the warming slowdown to be over,” Dr. Judith Curry, a Georgia Tech climate scientist who was not involved in the study, wrote in her blog.

“This is not necessarily the case; we will need at least another 5 years of observations to determine whether the slowdown is over and warming resumes at a pace of at least 0.2°C/decade, or whether the slowdown will continue for another decade or two,” she wrote.

Scientists have been struggling to explain why global temperature rise slowed down in the years after 1998, a period called the “slowdown” or “hiatus” in warming. It not only surprised scientists, but forced them to question the climate models used to predict future warming.

The climate warmed at about half the rate predicted by climate models since 2000, according to the NOAA study, which sought to answer the question of why the models were so far off. In the process, they suggest there’s a chance of no warming or even slight cooling in the future.

“Our analysis of model simulations suggest some conditions whereby an early 21st century global warming slowdown could potentially last much longer (to ∼2030) than is generally expected, as well as scenarios where a rapid temporary acceleration of warming might occur,” NOAA scientists wrote.

“The possibility of such behaviour in the climate system in coming decades, while not a prediction, should motivate more study of internal multidecadal climate variability and its mechanisms,” they wrote.

This isn’t the first study to look at the potential for a prolonged “slowdown” in global warming.

UK Met Office scientists released a study in 2015 claiming the probability of the slowdown lasting another five years was 25 percent. UK scientists found “the probability of a variability-driven 10-year hiatus is ~10%, but less than 1% for a 20-year hiatus.”

But that study was released before an incredibly strong El Niño warmed up the Pacific Ocean and drove up average global temperature to record levels for 2015. The naturally-occurring warming event persisted into 2016 and even had scientists freaking out over how warm it was in February.

Now, global average temperature is coming down as a relatively weak La Niña cooling event takes hold. The question on everyone’s mind is whether or not the “slowdown” will continue after El Niño’s heat fully subsides.

Lees verder hier.

Kortom, de wetenschap is er nog niet uit.

Voor mijn eerdere bijdragen over klimaat en aanverwante zaken zie hier, hier, hier, hier en hier.