We're Still On Track for the Hottest Decade on Record

Joe Romm

Solar cycle 24 revs up, though changes in the sun are increasingly a bit player in the global warming trend

Cycle 24

The 2000s were  the hottest decade in recorded history by far — even though we’re at “the deepest solar minimum in nearly a century.”  The 2000s were a full 0.2°C warmer than the 1990s, which of course had been the hottest decade on record, 0.14°C warmer than 1980s (according to the dataset that best tracks planetary warming).  Hmm.  It’s almost like the warming is accelerating.

Yet when the anti-science crowd isn’t perversely spending their time trying to stop all efforts to cut global warming pollution that might slow warming, they are perversely trying to convince the public and policymakers we’re not warming at all.  That’s why many of them have been rooting for this deep solar minimum to become a Maunder Minimum (”also known as the prolonged sunspot minimum”), to mute the warming signal and hence the motivation for action for a few more years.  Yes, they have a self-destructive streak.


In fact, even if total solar irradiance never recovered, we wouldn’t have entered a period of cooling since, “the negative forcing, relative to the mean solar irradiance is equivalent to seven years of CO2 increase at current growth rates,” as NASA noted in January 2009.  Heck, even with a La Niña and an unusually inactive sun, 2008 was almost 0.1°C warmer than the hot decade of the 1990s as a whole.  And 2009 was (just barely) the second hottest year on record after 2005.  And in spite of the unusual solar minimum, the past 12 months werer the hottest on record and “It is likely that 2012 will reach a record high global temperature,” according to NASA.

As far back as 2007, a Hadley Center paper in Science had concluded,

Our system predicts that internal variability will partially offset the anthropogenic global warming signal for the next few years. However, climate will continue to warm, with at least half of the years after 2009 predicted to exceed the warmest year currently on record.

So there’s little doubt the 2010s will be the hottest decade on record, barring multiple supervolcanoes, just as the 2000s and 1990s and 1980s were.

When we last looked at the sun [please, don't try that at home], NASA was reporting that the sunspot cycle was about to come out of its depression, if a newly discovered mechanism for predicting solar cycles — a migrating jet stream deep inside the sun — proved accurate (see National Solar Observatory, NASA say no “Maunder Minimum”).

Now, NASA has released a new “Solar Cycle Prediction” (see figure above):

Current prediction for the next sunspot cycle maximum gives a smoothed sunspot number maximum of about 64 in July of 2013.

Predicting the behavior of a sunspot cycle is fairly reliable once the cycle is well underway (about 3 years after the minimum in sunspot number occurs [see Hathaway, Wilson, and Reichmann Solar Physics; 151, 177 (1994)]). Prior to that time the predictions are less reliable but nonetheless equally as important. Planning for satellite orbits and space missions often require knowledge of solar activity levels years in advance.

A number of techniques are used to predict the amplitude of a cycle during the time near and before sunspot minimum. Relationships have been found between the size of the next cycle maximum and the length of the previous cycle, the level of activity at sunspot minimum….

We find a starting time of August 2008 with minimum occurring in November or December 2008 and maximum of about 66 in June of 2013. The predicted numbers are available in a text file, as a GIF image, and as a pdf-file.

And that means solar cycle 24 would be on the modest side compared to recent cycles.  But changes in the solar forcing just aren’t the big dog anymore when it comes to driving climate change, as I discussed here:  “A detailed look at the Little Ice Age.”

The Naval Research Laboratory and NASA reported last year that, “if anything,” the sun contributed “a very slight overall cooling in the past 25 years.” The study, “How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006,” found, “According to this analysis, solar forcing contributed negligible long-term warming in the past 25 years and 10% of the warming in the past 100 years.” A major 2007 study demonstrated “over the past 20 years, all the trends in the Sun that could have had an influence on the Earth’s climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.

Related studies can be found on Skeptical Science.  Dr. Bill Chameides, dean of the Nicholas School of the Environment at Duke University, has a good post on this subject, “The Waxing Sun and Warming Climate.”  Real Climate also has an interesting post, “Solar spectral stumper” on a study that would have important implications, if true, but which they doubt is true.

Bottom Line:  As long as we continue doing little or nothing to reverse global emissions trends, every decade this century is likely to (temporarily) hold the record for hottest decade.


This post was created for ClimateProgress.org         , a project of the Center for American Progress Action Fund    .  Joseph Romm is the editor of Climate Progress    and a senior fellow at the Center for American Progress.

Read more on Celsias:

The Global Impact of Ocean Cooling in the 1960's

2010 on Track to be Warmest Year on Record

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  • Posted on Oct. 12, 2010. Listed in:

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