Sunday, January 18, 2015

2014's Warmth Record All Due to Sun*

(*) see below

2014's record warmth was all due to the Sun*. The Sun's radiance has increased since 2010, the last surface temperature record that was set.

LASP in Colorado (Laboratory for Atmospheric and Space Physics) gives a daily measurement of Total Solar Irradiance (TSI) -- the energy, per unit area, that the Sun emits. They give it at both the position of the Earth, and at 1 AU (astronomical unit -- the Earth's average distance from the Sun).

If you want to look for changes in TSI, it's best to use the 1 AU data, to avoid any complications with the Earth's orbital factors (though between 2010 and 2014 those shouldn't matter).

Downloading the data, I find the average TSI at 1 AU has been

where TOA = Top Of the Atmosphere. Annual TSI has increased by 0.57 W/m2 from 2010 to 2014. That's a fairly healthy increase -- 2014 was the top of the current solar cycle....

even in historical terms:

(Yes, some of the data are missing for each year, especially 2014. I could interpolate over the missing days, or some such blogger-like thing, but I'd be surprised if it mattered much. LASP's annual number will eventually appear here.)

So what's the effect of this increase in TSI over the last four years?

You can estimate the impact of TSI changes for the surface temperature; it's

∂T/∂L = T/4L = 0.05°C/(W/m2)

where L is the Sun's TSI (luminosity). This is just a differentiation of the basic equation for equilibrium: energy coming in from the Sun = energy radiated out by the Earth:

$$  P_{in} = \pi R^2  (1-\alpha) F_0,$$ = $$ P_{out} ==  4 \pi R^2 \epsilon \sigma T^4. $$

where I'm stealing some equation JPGs from Nir Shaviv, who has a nice little discussion about all this. (BUT, be careful of his notation versus yours - he calculates temperature change as a function of solar irradiance at the surface, not the top of the atmosphere.) Plugging in the number for the change in TSI, we get

ΔT = 0.03°C

from 2010 to 2014. Which more than explains the 0.02°C increase seen in the GISS data (though not quite the 0.04°C in the NOAA data).
(*) Now for the asterisks.

OK, I'm being somewhat facetious, and the above should be taken with a grain of salt -- it's just a quick estimate -- but the point is, the observed increase since 2010 isn't obviously from greenhouse gases. And the point of that is the simplistic notion, which by now is probably appearing in kindergarten newsletters to parents and in fortune cookies baked just for the occasion, that 2014 was definitely warmer than 2010 definitely due to greenhouse gases definitely due to man and his definite burning of fossil fuels.  

It's not a particular year that matters, it's the long-term trend. But that doesn't make for a great headline (unfortunately).

I mean, don't get me wrong -- I certainly think the long-term trend is troubling, and due to GHGs, though I don't know if this will all end up being catastrophic (whatever that means). I think super-hyping a particular year because it's a couple hundredths of a degree warmer misses the whole point, as well, as I wrote earlier, opening the door for the same tactics from the Joules/second of the world. 

Obviously everyone -- the media, the public information community, some scientists -- are hawking this because it's dramatic and offers at least a clear moment to draw a great deal of attention on the issue of AGW, which long-term trends don't (unfortunately). It's a chance to stick it back to the deniers and idiotic Congresspeople; as Eli Rabbet commented awhile back
Patience is a virtue. The whole thing is weird. El Nino, melting of the Artic, etc, are not things to wish for, but the horse shit is so deep you almost want these things to happen to to shut the fools up and get people to pay attention. Sucks to be human. . . . Wait. 
Much the same here -- it's tempting to make a big deal out of 0.02°C, because of all the horseshit, and because too few of the public (American at least) understand enough to make sense of anything else. 

So I guess all I'm saying is that by now I think all the "2014 was the warmest year in recorded history" is very misplaced, and it's sad that mainstream journalists either think they have to write such things as the only way to inform the public, or that that's all the journalists themselves can understand, or because they themselves are activists. To not at least mention the relative probabilities for the hottest year, given in the NOAA/NASA press conference -- is inexcusable.

I'll let Gavin Schmidt, now NASA GISS's director, have the last word:

1 comment:

Victor Venema said...

A record normally has multiple causes. To set the marathon world record, you need a good runner, having a good day, on a flat course that goes down just as much as still allowed and the perfect weather.

Without the 1 degree temperature rise since 1880 due to greenhouse gasses, the sun could have jumped up and down, but would not have produced this record. Noise or other influence factors are no reason not to call a record.

That the press has this bizarre need for a current hook to write an article is one of the big problems of humanity that you and your colleagues will have to solve.