Friday, April 24, 2015

A Surprising Temperature Reconstruction, 100-2000 A.D.

There's a surprising paper in Geo Rev Letters, presenting this reconstruction of surface temperatures over the last 2000 years. I've taken the data and calculated its 10-year moving average:


Not surprisingly, it finds a warm Roman period, but then the reconstruction shows a dip in temperatures during the Medieval Climate Anomaly (MCA) of 1000-1200 AD. Then mild temperatures, then a sharp dip into the Little Ice Age, and strong warming since 1850 and the Industrial Revolution.

Not too surprising, except for the MCA. How did that come about?

--

Well, in fact it did not come about. Actually, this data consists of nothing but random numbers that I generated, between 0 and 1, one per year, with their 10-year moving average plotted above.

How do random numbers give a realistic looking temperature time series?

It's called the Slutsky Effect, which I just learned about from an article John Fleck sent me a few weeks ago:

"The myth of Europe’s Little Ice Age"
Morgan Kelly, Cormac Ó Gráda, 28 March 2015

Eugen Slutsky (1880-1948) was a Russian mathematician who did important work in economics and in the mathematics of time series, while trying to keep his head on his shoulders during the Russian revolution and the murdering afterward.

Slutsky showed that it's very easy to construct random times series that appear, when a moving average is calculated, to give results very reminiscent of economic business cycles. Here is a nice overview.

Or, here, a temperature time series.

The random data I generated, between 0 and 1, has an average of 0.490 and a standard deviation of 0.025.

Its trend from start to finish is -0.000003 -- essentially zero. Yet it shows what could easily be interpreted as meaningful intervals of warm and cold.

Kelly and Ó Gráda look at temperature reconstructions in Europe from 1300-2000, calculated 25-year moving averages, and find the following:



which looks meaningful, except it comes from this raw data, whose trend isn't statistically different from zero:


They've done more statistical analysis in a paper in the Annals of Applied Statistics, which I have not yet read but plan to.

So what to make of this?

I'm not sure. Patterns can be found in random data, that look meaningful. A series of random events can combine to look like a meaningful cycles in an economy, or a climate.

Is this all that modern global warming is, a time series analyzed so as to look meaningful? No, because its trend is statistically different from 0.

But other data? I think the lesson is you need to be careful. Kelly and  Ó Gráda conclude there was no Little Ice Age, in a statistical meaningful sense. There were, to be sure, decades of worse weather than normal, that affected crop production in regions and the people who depended on them.

But a widespread LIA? They say no.

More later.

For me this glass is already broken.

"You see this goblet?" asks Achaan Chaa, the Thai meditation master. "For me this glass is already broken. I enjoy it; I drink out of it. It holds my water admirably, sometimes even reflecting the sun in beautiful patterns. If I should tap it, it has a lovely ring to it. But when I put this glass on the shelf and the wind knocks it over or my elbow brushes it off the table and it falls to the ground and shatters, I say, 'Of course.' When I understand that the glass is already broken, every moment with it is precious."
via Kottke.org

Smoking Them Out, One at a Time

A correction in Newsweek:


Here is the good Dr. Simmons, another one who won't disclose.

Tuesday, April 21, 2015

Is it Fair to Now Blame China for Climate Change?

Perhaps in advance of the Paris conference this December, a spate of articles came out in the last few days claiming that "China to surpass U.S. as top cause of modern global warming." Is that fair? (No.)
(Reuters) - China is poised to overtake the United States as the main cause of man-made global warming since 1990, the benchmark year for U.N.-led action, in a historic shift that may raise pressure on Beijing to act.

China's cumulative greenhouse gas emissions since 1990, when governments were becoming aware of climate change, will outstrip those of the United States in 2015 or 2016, according to separate estimates by experts in Norway and the United States.

The shift, reflecting China's stellar economic growth, raises questions about historical blame for rising temperatures and more floods, desertification, heatwaves and sea level rise.
and
"A few years ago China's per capita emissions were low, its historical responsibility was low. That's changing fast," said Glen Peters of the Center for International Climate and Environmental Research, Oslo (CICERO), who says China will overtake the United States this year. 
Here's data on US and China cumulative emissions since 1990:


Yes, by this measure China will surpass the US by about 2016.

But, of course, the climate doesn't care about your silly accounting choices and conferences, it only knows how much CO2 is in the atmosphere. And the US has emitted a lot more CO2 over the last century than has China. Since 1900, the comparison comes out very nicely if you take the ratio of cumulative emissions:


CO2 emissions data: 
1900-2004 from World Resources Institute
2005-2012 from EIA
2013 from the Carbon Atlas Project
2014 from the EIA (for the US) and reported percentage increase in China (-2.0% compared to 2013).

That's not even to mention per capita emissions, which in 2014 were 16.9 tons CO2/person in the US and 7.2 tons CO2/person in China.

GCP Per Capita Consumption Emissions

And in 2012, 16% of China's emissions went to products exported elsewhere (not sure of this number for the US).

Ukcarbonexports7

Many like comparing national emissions, but it's not like an American has some exceptional right to emit CO2 that a Chinese citizen does not. We're the world's energy hogs, not them. And China's one-child policy probably did more to reduce emissions than all of the Kyoto Protocol.

(In James Hansen's book he writes that it's actually the UK that has the highest historical per capita emissions, but IIRC doesn't provide a source for that.)

So I don't think it's fair to start blaming China for global warming -- not even by 2025, when their cumulative emissions are projected to pass the US's (see above). But that seems like what some are trying to do already.

 GCP Territorial Emissions

 Figure via The Carbon Brief.

Saturday, April 18, 2015

More About Cumulative Warming, Models versus Observations

This is more about how well (or not) climate models predict/project the total warming that's been seen so far.

After I put up this graph of a GISS model's cumulative warming versus observations, a couple of people said "but it's just one model." Fair enough. It happened to be the first model I looked at, because I'd been reading a paper about it.

The same CMIP5 page also has a data file for an ensemble of 21 model -- presumably, the "best" ones, the biggest ones, made by the big research groups. (All models aren't created equal, which makes one wonder about this Roy Spencer graph with an average of 90 models. More about that graph at HotWhopper.)

Here's the result for the total warming from 1860 to 2014:


C&W is Cowtan and Way. Again, by "total warming" I mean (linear slope)*(time interval). (Not perfect, but what would be better? Maybe average_of_last_30_years - average_of_first_30_years. Maybe I'll try that later.)

So, the agreement is pretty good. The deviation between the ensemble mean and Cowtan & Way starts around 2005, and is now up to 0.07°C. There's your slowdown.

If I was Stephen Koonin, I would say the model error is only 0.07 K/288 K = 0.02%. But I'm not, so I won't.

Instead, it's about 0.07 K/0.94 K = 7%, over a century and a half.

So how good does a model need to be?

Friday, April 17, 2015

NOAA Gets Warmer

NOAA found the average global temperature anomaly for March to be the warmest for any March in their records, and the third-warmest of any month since 1880 (after only the tie between Feb 1998 and Jan 2007).

Here's how warm it's been in recent months: NOAA's record year was also 2014, with an average anomaly of +0.69°C. For this year to match that record, the rest of 2015 has only to average +0.65°C, which is 0.17°C below what's it's averaged so far.


Note: NOAA uses a baseline of 1901-2000, so their numbers aren't directly comparable to GISS (1951-1980) or HadCRUT4 (1961-1990). But trends are directly comparable, as are differences between months.

Thursday, April 16, 2015

Tuesday, April 14, 2015

See Steyn Lie

In another post by a climate expert, Mark Steyn writes:
"As I've said before, if you graduated from college last summer, there's been no "global warming" since you were in kindergarten."
This is getting so bad now this can only be called what it is: a lie. Purposeful deceit. Scientific fiction.

Blatantly, it ignores ocean warming, the best of all indicators of global warming. (As they say, it's called "global warming," not "surface warming" and not "only-RSS-and-no-other-datasets-allowed warming.")

The correct statement is:
If you graduated from college last summer, you've just lived through the warmest 12 months of your life. And of your parents' lives, and your grandparents' too.
I hesitate to confuse Steyn with numbers, but... assuming one is 5 years old in kindergarten, and 22 when they graduated college last summer (so most people would be 23 at this piont), that's the cherry picked "18 years."

So let's look at NASA GISS's temperature anomaly since Jan 1997:


Or this, showing the last 12 months are the warmest such period in GISS's records:


Of course, those looking to fool others like to pretend the only data that exists anywhere in the world is from RSS:


while completely ignoring the other data that measures the same thing, but which has better coverage of the globe (UAH misses 0.9% of Earth's surface; RSS misses 6.9%).


I won't even get into error bars and statistical significance and all that -- it would pass through Steyn as just more dark energy. Or Cowtan and Way (trend of +0.11 C over 18 years.) Or ocean warming, the best of all indicators of global warming. Or the role of natural variability, or that 18 years is too short to be indicative of climate change anyway. 

The liars like Mark Steyn don't want to hear anything about all that. Climate science is, for him, just another thing to hate on, another faucet for his bile.

What Hiatus?


Data:
http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt

NASA GISS: March was 5th Warmest Month in Their Record

GISS's March anomaly was +0.84°C, the 5th warmest (most anomalous) month since 1880.

It was the 3rd warmest March. The Northern Hemisphere (+1.17°C) was the warmest March in the records, and the second-highest of any month in the NH.

My guess (+0.86°C) was again pretty good.

Recent temperatures are climbing, and now approach the peak of the 1997-98 El Nino:

Nino3.4 anomaly on left-hand axis; GISTEMP anomaly on right-hand axis.

April 2015, however, is looking like it will have a signficant anomaly drop of perhaps 0.2°C - 0.3°C, based on the first half of the month. More on that later.