Sunday, June 26, 2016

You Too Can Calculate the Earth's Energy Imbalance

Last week Gregory Johnson et al published a new number for the Earth's energy imbalance in Nature Climate Change: a net heat uptake from 2005 to 2015 of

0.71 ± 0.10 W/m2.

Globally that works out to 360 trillion Watts, or 50,000 Watts per human!

They broke this down as follows:

0.61 ± 0.09 W/m2 taken up by the ocean from 0–1,800 m
0.07 ± 0.04 W/m2 by the deeper ocean, and
0.03 ± 0.01 W/m2 by melting ice, warming land, and an increasingly warmer and moister atmosphere.

So 86% of the extra AGW heat went into the top 1800 meters of the ocean. Plus or minus.

(Note: The global energy imbalance is not global radiative forcing. RFs are calculated and measured at the tropopause; global energy imbalance is with respect to the top of the atmosphere. And there are warming and cooling factors besides radiative forcings from greenhouse gases, like changes in solar irradiance, manmade and volcanic aerosol emissions, brown carbon, etc., and maybe even waste heat.)

You can easily get a good estimate of this energy imbalance number by using NOAA's data on ocean heat content from the Argo buoy network. The 0-2000 meter ocean heat content data the is here -- I find its linear trend to be, from 1Q2005 to 4Q2015,

0.66 ± 0.04 W/m2.

Pretty close for blog work -- within 10%. A little higher then their value for the ocean -- perhaps since I included an extra 200 meters -- and a little lower than the total value including everything.

Some points:
  • I used the data for the top 0-2000 meters of the global ocean. Not sure why they only used 0-1800 meters. (Incidently, the average depth of the ocean (= volume/area) is 3,682 meters, so you can say they measured the top half of the ocean.) 
  • I ignored (obviously) heat going into the ocean below 2000 meters, or into melting ice and the other small contributions. (I'm surprised that the deep ocean's energy gain is over 10% of the 0-2000 m region.) 
  • I divided the 0-2000 ocean heat gain by the Earth's entire surface area, since the vast majority of the heat goes into the ocean.
  • My uncertainty was just the simple standard error from linear regression, i.e. no autocorrelation or anything fancy.
The data in the figure above clearly looks to now be increasing faster than linearly. If I regress the data to a 2nd-order polynomial, I get an acceleration of the energy imbalance of +0.09 W/m2 per year.

In 2012 Loeb, Johnson and others published a global energy imbalance of 0.50 ± 0.43 W/m2 for the period Jan 2001 to Dec 2010. (Note the first half of this period was before the 0-2000 m Argo data became available in 1Q2005; I guess that's why the uncertainty has dropped so much.) For a reason that escapes me, the latest paper says their previous estimate was 0.58 ± 0.38 W/m2.

Using their former number, that gives a change in global energy imbalance of 0.71-0.50 = 0.21 W/m2 in five years, or an acceleration of about 0.04 W/m2 per year. A 40% increase in just 5 years.

That's about half my number (not sure why). But as an acceleration, neither number can be dismissed as insignificant.

Added: ATTP has some thoughts on the implication for climate sensitivity and Lewis & Curry preprint.

Sunday, June 12, 2016

More About Anomalies and Normal Distributions

Some followups to my post of last night.

First, I made a spreadsheet error on the HadCRUT4 monthly anomalies that slightly inflluenced the result. I replaced the plot with the corrected one.

Second, it was requested that I slso do a histogram for the annual anomalies, since that was being discussed. It's also clearly not normally distributed:


Third, a Twitter response to last night's post pointed to this post by Andy Cotgreave, who created this nice graph, which shows how the distribution has been changing over time, shifting to higher temperatures:


There are more good graphs on his post.

Saturday, June 11, 2016

Are Global Temperature Anomalies Normally Distributed?

There is some discussion elsewhere here about what weather and climate numbers are normally dististributed and what aren't.

I don't know if one can say a priori if a normal distribution is expected. But the fact is many sets of numbers from different fields are normally dististributed, but many aren't.

There are statistical tests for normalcy that you can apply to your data, which I'm not going to do here. I'll just present two plots.

The first is the average daily temperature in my town of Salem, Oregon. I've been collecting it daily since I moved here in September 2012, and was able to easily obtain the numbers for the 12 months prior. Here's a histogram of the distribution of the day's deviation from average (defined over the interval 1981-2010).


The bins are 0.5°F wide, and instead of plotting the count of the number of temperatures in each bin I've plotted the percentage of them amount the total. It looks fairly Gaussian (="normal"), but with the peak count shifted a couple of degrees to the right, which I assume is global warming.

Then I've plotted the monthly anomalies for HadCRUT4 over the length of their record, which starts in January 1850 (6/12 8:30 am PT: this has been corrected since the original last night; the results didn't change sustantially):


These data clearly aren't normally distributed. The long length of the record, most of which is before the sharp change in manmade global warming in 1975 or so, skews the dataset.

It's late and I'll try to write more about this tomorrow. Corrections and comments welcome.

Friday, June 10, 2016

Best Short Introduction to Climate Science That I Know Of

I don't know if I've ever mentioned this before, but if you're looking for a quick but firm introduction to the science of climate change, the best six pages I know of are Raymond Pierrehumbert's 2011 article in Physics Today, "Infrared Temperatures and Planetary Tempertures."

It's his book boiled down to the basics. To really understand it you'll need to understand college freshman-level physics, but if you do, or you know anyone in that situation who is looking for a succinct but accurate introduction, this is what you should give them, in my opinion. Others will get good things out of it too.

Hurricanes, This Year and Last

Peter Sinclair has a nice video up at Yale Climate Connections about last year's record-breaking season, and the prospects for this year if a La Nina develops:


Some highlights:
  • Last year (2015) was the most active hurricane year on record, in terms of Category 3+ hurricanes, according to Kevin Trenberth. ("Typhoons" are just another name for hurricanes, occurring outside the North Atlantic).
  • The odds of Florida being hit by a hurricane about about twice as much during La Nina years as during El Nino years.
  • More than half the hurricane damage done in the US since the mid-19th century has come from just 8 events.  
Ryan Maue tabulates ACE values (Accumulated Cyclonic Energy) on a monthly basis here, and a year-to-date basis here.

So far he only has monthly ACE values through September 2015.

I've been trying to record the YTD values on a weekly basis since March 2014. From that I can estimate the monthly values (but not calculate them exactly). When I use that data for estimations of Oct-Dec 2015, I get a global ACE value for 2015 of 1049, in whatever stupid units they use (10,000 knots-squared), which would be the third-highest annual total since 1970 (1992 is first, and 1997 second).

As I've written about before, ACE isn't a great metric, because it does not consider the size of a storm. (It's like calculating the kinetic energy of a moving object without considering the mass of the object!) Two summers ago at an NCAR science journalism workshop in Boulder, on a van ride back from Rocky Mountain National Park, I had a good long talk with a world-renowned hurricane expert (off the record, so I can't name her/him), but s/he told me ACE is about the worst metric out there.

Much better is TIKE - Track Integrated Kinetic Energy. But I haven't seen that calculated on a regular basis anywhere. But I did write about it here for the 2013 North Atlantic hurricane season.

2012's Hurricane Sandy had a higher TIKE value than any other tropical storm or hurricane in the North Atlantic Ocean Basin since 1990. 

Wednesday, June 08, 2016

Read the Stanford Rape Victim's Statement

If you were thinking, like I was, that maybe the 7,250 word statement from the rape victim of Brock Turner wasn't worth the time, I hope you set that aside and read it anyway.

It is a powerful piece of direct honesty and bare bravery.

My emotions caught in my throat when I read the last paragraph. It is so noble, so determined, so unbelievably courageous that I have to reproduce it here.


I still can't read this without getting chocked up. It is one of the most profound things I have ever read.

Tuesday, June 07, 2016

The Gateway to the Underworld

This massive crater -- Batagaika crater, or what local people call the Gateway to the Underworld -- appeared in Siberia 25 years ago after trees were cut in the 1980s or early 1990s. (Cutting down vegetation reduces insulation of the soil, leading to permafrost melting.) This crater is a kilometer long and 90 meters deep, and is widening by up to 20 m/yr. Such crater are called "megaslumps."


The Independent has another amazing picture of a geologist standing at the base of the cliffs.