Sunday, August 30, 2015

What are the odds that 2015 will not be the hottest year on record?

Let me be upfront with you: I think it's a foregone conclusion that 2015 will beat out 2014 as the hottest year on record. However, I decided to test that idea, just to be certain.

The way I did it was simple: I first calculated the year-to-date average (January - July) and then calculated what the August — December average would have to be to keep the 2015 average temperature at or below that of 2014. I then calculated the August — December average for each year since 1970, fitted a trend, and calculated the standard deviation of the residuals. Last, I calculated the expected August - December average for 2015 given the trend and the difference between the expected August - December average and what that average would have to be to keep 2015 from setting a new record.  I then used z-scores to calculate the probability that the remainder of 2015 would fall to that level or below.

Annual global temperature according to NASA GISS since 1970

Year to date, 2015 sits at +0.82ºC above the 1951-1980 baseline.  The average for 2014 was "only" +0.75ºC above the baseline.  Keeping 2015 at or below the standard set by 2014 would require an average temperature of at most 0.652ºC for the remainder of the year.  So, how likely is that average temperature for the August - December period?
Average August - December temperatures since 1970.
The predicted average for August - December 2015 based on the trend would be 0.772ºC, more than enough to make 2015 the hottest year on record.  With a standard deviation of 0.0981ºC, there is only an 11.05% chance that the August - December 2015 average would be at 0.652ºC or below.  This means that right now, 2015 has at least an 88.95% chance of breaking 2014's record.  Pretty good odds but not quite a foregone conclusion.

There is one important caveat that means that I overstate the chance that 2015 will not break the record: I did not account for El Niño years.  That was done deliberately.  I wanted to be conservative with my estimate.  With a strong and strengthening El Niño event in the Pacific that might rival the 1983 and 1998 El Niños, I personally believe that 2015 has a nearly 100% chance of smashing 2014's record baring a major volcanic eruption.

Saturday, August 8, 2015

Global warming, The Wall Street Journal, and John Gordon

John Steele Gordon published a commentary in The Wall Street Journal on July 30 that, on its face, sounds reasonable.  Gordon makes the case that we should be cautious about calling climate science settled as science is always changing.  No real quibbles there, as science has shown that nothing is ever truly "settled" science.  Unfortunately, that's as close to reality as Gordon comes.  The rest of the commentary simply shows off Gordon's simplistic view of history, science, and, especially, the current state of climate science.

Saturday, August 1, 2015

Hottest first six months on record

I know, I know, I'm behind a bit.  Most of the stories on the first six months of this year came nearly a month ago.  Better late than never.  By now, we all know that the world is headed toward its hottest year ever, breaking the record set just last year.  In this post, I'm going to analyze just how abnormal normal the first half of the year has been.

Thursday, July 30, 2015

James Taylor gets polar ice wrong—as usual

James Taylor of the Heartland Institute had a piece on Forbes back in May that escaped my attention when it first came out.  Titled "Updated NASA Data: Global Warming Not Causing Any Polar Ice Retreat", it focused on the single premise that since 2012, total polar sea ice was above the average since 1979.  Taylor then jumped to the erroneous conclusions that a) polar sea ice was not retreating and b) global warming will be entirely beneficial to humans.  His arguments are familiar, as I dealt with them before when a Newsmax article featured them back in 2014.  He's recycling old talking points, so this post is going to echo the one I wrote a year ago.

Wednesday, July 22, 2015

The Ice Age Cometh?

Recent media reports have claimed that a drop in solar activity will lead to a mini-Ice Age within the next 15 years.  Unfortunately, even press reports from science-related media such as Science Daily, have been riddled with errors.

Let's get the biggest one out of the way first.  Zharkova et al. (2015) did not predict a new Little Ice Age (LIA).  What they did was use principle component analysis to detect and model magnetic waves within the sun.  They found that there were two such waves, each with an 11-year cycle, that either interfered with each other when sunspot activity was low or magnified each other when sunspot activity was high.  They then ran their statistical model ahead to make a prediction for the next solar cycle and found that their model predicts that the waves should cancel each other out, resulting in their subsequent prediction that solar activity should drop to levels not seen since the Maunder Minimum.  That bit about the Maunder Minimum is what set off the media, as the Maunder Minimum coincided with the coldest time period of the Little Ice Age.

Unfortunately for the journalists and editors who made that connection and then made the claim that a new Little Ice Age would begin within 15 years, they are dead wrong.  First, multiple research papers have found that a new Maunder Minimum would shave a maximum of 0.3ºC off the expected rise in global temperatures by AD 2100 (Feulner and Rahmstorf 2010, Jones et al. 2012, Anet et al. 2013, Meehl et al. 2013).  So the world would warm by "only" 3.7ºC rather than 4ºC.  Furthermore, the impacts would be largely regional, not global, and temporary.  Ineson et al. (2015) found that the greatest cooling would fall on Europe and the eastern US during winter but that global temperature as a whole could be largely unchanged.  Once the new minimum ended, regional temperatures would warm back up.

Second, solar activity decoupled from global temperature in the 1970s.  Solar activity peaked in the late 1950s and then again around 1980 and has declined sharply since whereas global temperatures rose.  In short, global temperatures are controlled by something other than solar activity now.

Third, research shows that the Little Ice Age began and was sustained by volcanic eruptions, not solar activity (Miller et al. 2012).  And contrary to the Science Daily article, the LIA began in AD 1300, not AD 1645 as that article wrongly claimed.  The timing of the Maunder Minimum, coinciding with the coldest part of the LIA, gave the false appearance of a link between the two.

Fourth, there is a lot more CO2 and other greenhouse gases in the atmosphere now than there was during the Maunder Minimum.  The 12-month moving average for CO2 is now 399.34 ppmv.  Pre-industrial CO2 levels were around 280 ppmv, which means that there is now 1.89 W/m2 of extra energy being trapped by Earth's atmosphere that wasn't there during the Maunder Minimum.  That translates into a temperature rise of 1.53ºC, greater than the drop the Earth experienced during the Maunder Minimum.

Last, the Little Ice Age was just that—little on the global scale.  Using the global data from Marcott et al. (2013), the Little Ice Age was a mere blip compared to how temperatures have risen since.

Global temperatures over the LIA declined by about 0.2ºC over 550 years.  Temperatures have risen by 0.8ºC in the 160 years since the LIA ended.  Even if we did have another LIA, then all it would do is return global temperatures to about where they were around 1980, which is a far cry from where they were during the Maunder Minimum.

To sum all of this up, there is no new ice age coming, even if the sun does repeat the Maunder Minimum.  Instead, we can expect temperatures to continue rising as CO2 levels increase due to the 30+ billion metric tons of CO2 we spew into the atmosphere each year. 

Likely global temperature rise in the near future. The thick dashed line represents the continuation of the trend. The thinner dashed lines mark one standard deviation and two standard deviations from the trend, respectively.

Abraham Lincoln once quipped that his opponents "had their facts absolutely right but were drawing the wrong conclusion."  Those journalists who wrote that another mini-Ice Age was coming not only drew the wrong conclusion—they also got their facts absolutely wrong.

Tuesday, July 21, 2015

US versus global temperatures

One of the talking points I see (and hear) time and again here is the question "If the world's getting hotter, why is it cold here?", "here" usually referring to the eastern United States.  Another variation goes "Global warming can't be happening because US temperatures haven't risen in _____ years."  Yes, it's the good old "It's cold in my backyard so the planet can't be warming up" argument. Here's why it's dead wrong.

Friday, June 5, 2015

The "hiatus" doesn't exist.

That is the conclusion of a new study published in Science yesterday.  Tom Karl and his co-authors used a newly available database of weather station data that combined the Global Historical Climatology Network (GHCN) used by NOAA and NASA with over 40 other historical data sources, effectively doubling the size of the available land temperature data set.  They applied the same corrections for changes in location, urban heat island effect, etc as with the GHCN-only data set and used the same algorithms to calculate the global average over land.  To get a global average, they used the Extended Reconstructed Sea Surface Temperature dataset version 4 (ERSST4), which better integrates ship-based temperature data and buoy-based temperature data, and merged it with their new land data.  Karl et al. then created a third global temperature average that also fills in the gaps between weather stations in the polar regions.

Their new data set shows much higher trends than the GHCN-only data, especially since 1998.  Their analysis shows >2x the warming since 1998 (0.086ºC/decade) as the GHCN-only data (0.039ºC/decade).

Figure 1 from Karl et al. 2015 showing the trends over selected time periods as calculated using GHCN-only data (circles), their new data (squares), and their new data combined with polar interpolation (triangles).
This is mostly due to a much higher sea surface average (0.075ºC/decade versus 0.014ºC/decade) since 1998.  The upshot is that there is no statistically difference between the 1951-2014 warming rate and the 1998-2014 warming rate, meaning that the so-called "hiatus" does not exist.

The main conclusions from Karl et al. is that the appearance of a pause was due to a) a short time period (changing the period by just two years had a significant impact on the calculated trend) and b) a cherry-picked start year (1998, the warmest El Niño currently on record), and c) artifacts due to incomplete data.  This matches the main thrust of other research into global temperature data (i.e. Foster and Rahmstorf 2011, Rahmstorf et al. 2012, Rohde et al. 2013, Cowtan and Way 2014, the various Berkeley Earth papers) and various blog posts (i.e. Tamino and my own writings).

The "pause since 1998" is dead.  Long live the "pause since ______" that deniers come up with next.