Yes, the globe is warming. But how fast?

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"Yes, the globe is warming. But how fast?"

In a world of complete knowledge, we could measure annual temperatures around the globe and then factor out all of the short-term changes not driven by human emissions. What’s left would be the anthropogenic or human-caused global warming trend.

In the real world, however, we don’t measure temperatures everywhere — we interpolate between temperature stations. And we don’t know the exact magnitude of all the short-term natural variability. That leaves plenty of room for global warming deniers and delayers to intermittently push their siren song of “global cooling” (see “Media enable denier spin: A (sort of) cold January doesn’t mean climate stopped warming“). And siren song it is (see “Hadley Center to delayers: We’re warming, not cooling” and “Hansen throws cold water on cooling climate claim” and “Breaking News: The Great Ice Age of 2008 is finally over — next stop Venus!“).

In this post, I will examine some of the factors that have affected recent temperature records (including changes in solar irradiation) to understand what is really going on. First, RealClimate’s Gavin Schmidt has extracted the the El Ni±o – Southern Oscillation (ENSO) signal from the global temperature data (both NASA’s and Hadley’s):

enso_corr.jpg

Gosh, it’s warming. Who would have thunk it?

[For more on the ENSO factor, time series smoothing, and global warming, read “Has the world cooled since 1998?” (pp. 141-148).]

You may wonder why NASA shows more warming in recent years than the Hadley Center. The answer is quite important to this discussion. As Schmidt explains, the Arctic Ocean has no temperature station coverage:

[Hadley] does not extrapolate past the coast, while [NASA] extrapolates from the circum-Arctic stations — the former implies that the Arctic is warming at the same rate as the rest of the globe, while the latter assumes that the Arctic is warming as fast as the highest measured latitudes.

Since the Arctic appears to be warming up at an alarming rate — far faster than the rest of the globe, as the literature had predicted — I find the NASA data more compelling. Indeed, if anything, even the NASA dataset probably underestimates the recent warming, since the temperature above an ice-covered Arctic Ocean can get very, very low (many tens of degrees below 0ºC), whereas the temperature above open ocean (or thin ice) is close to 0ºC).

Significantly, The ENSO is not the only ocean-based source of temperature fluctuation:

THE PACIFIC DECADAL OSCILLATION

The PDO is not as well understood as ENSO, but it may be as important. Here is the the PDO’s monthly values since 1900:

pdograph533.jpg

Note: William Patzert of NASA’s Jet Propulsion Lab commented on Andy Revkin’s recent post, “Climate Trends With Some ‘Noise’ Removed,” that “the PDO index above is the result of analysis in which any long-term climate trend is removed.”

JPL’s Patzert and Willis (here) explain that

We still don’t really know what causes the PDO. We can see it in the data, but we don’t have a physical explanation for what is driving it. Until we do, we can’t really say what the interactions between global warming and the PDO are.

That said, during long periods of negative PDO, the rate of global warming is slower, and during positive periods of the PDO, the rate of warming is faster.

If we are entering a negative PDO, that could slow the rate of global warming. As Willis and Patzert note, notwithstanding the natural short-term oscillations in the temperature record, the overall temperature increase is pretty obviously caused by human activities. Here is the full NASA record:

nasa-2007.gif

HERE COMES THE SUN?

The favorite denier notion that the Sun is responsible for the global warming of the past century. That myth has been long debunked — see see “Fred Thompson, Global Warming Denier and Sun Worshiper” and Skeptical Science and AMS Seminar and RealClimate. Indeed, a major 2007 study in the Proceedings of the Royal Society concluded:

Here we show that 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.

That said, the Sun does have a well-known short-term irradiance cycle. As NASA explains:

The sun is another source of natural global temperature variability. Figure 3, based on an analysis of satellite measurements by Richard Willson, shows that 2007 is at the minimum of the current 10-11 year solar cycle. Another analysis of the satellite data (not illustrated here), by Judith Lean, has the 2007 solar irradiance minimum slightly lower than the two prior minima in the satellite era.

nasa-solar-fixed.jpg

Figure 3. Solar irradiance from analysis of satellite measurements by Willson and Mordvinov (Geophys. Res. Lett. 30, no. 5, 1199, 2003) and update (private communication). Click to enlarge.

This cyclic solar variability yields a climate forcing change of about 0.3 W/m2 between solar maxima and solar minima…. Several analyses have extracted empirical global temperature variations of amplitude about 0.1°C associated with the 10-11 year solar cycle, a magnitude consistent with climate model simulations….

The solar minimum forcing is thus about 0.15 W/m2 relative to the mean solar forcing. For comparison, the human-made greenhouse gas climate forcing is now increasingly at a rate of about 0.3 W/m2 per decade. If the sun should remain ‘stuck’ in its present minimum for several decades, as has been suggested in analogy to the solar Maunder Minimum of the seventeenth century, that negative forcing would be balanced by a 5-year increase of greenhouse gases. Thus such solar variations cannot have a substantial impact on long-term global warming trends.

CONCLUSION

The solar cycle has dropped temperatures about 0.1°C in the past decade. ENSO added about 0.15°C to the 1998 peak. The PDO may be having an effect now but its magnitude is uncertain. If we subtracted out all of that “noise,” human-caused global warming appears to be about 0.1°C to 0.2°C a decade as predicted.

The greenhouse gas forcing will increasingly dwarf the natural forcings in the coming years and decades. Absent a major volcano, we will probably see record temperature growth in the 2010s, as two recent major studies concluded, see “Nature article on ‘cooling’ confuses media, deniers: Next decade may see rapid warming” and “Climate Forecast: Hot — and then Very Hot.” Then the “global cooling” meme will disappear forever, to be replaced by the “global desperation” meme, which I call Planetary Purgatory.

This is particularly true if the Arctic goes ice-free in the next decade, which seems increasingly likely. And if that causes accelerated methane emissions from the tundra, then all model forecasts of future temperature rise go up in flames (see “Tundra 4: Permafrost loss linked to Arctic sea ice loss“).

If the short-term temperature fluctuations of the last few years lead us to another decade of inaction, then we are headed to 1000 ppm this century — and that means warming for the rest of this century will average more than 0.5°C a decade (see “Nature publishes my climate analysis and solution” and “Is 450 ppm politically possible? Part 0: The alternative is humanity’s self-destruction“). The implications are staggering: By mid-century, the planet would be warming each decade as much as it warmed in the past half century.

The time to act is yesterday.

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24 Responses to Yes, the globe is warming. But how fast?

  1. paulm says:

    Looking at this analysis you have to say that in the next few years when the sun’s forcing starts to increase and we get an el nino, then the permafrost methane tipping point is inevitable. This pretty much means that we are heading for runaway global warming in the next decade. I think we are past the grand daddy of the sum of the GW tipping points. There is no turning back now. Lets hope the tipping point for an ice age kicks in.

  2. Badgersouth says:

    Joe: When you post an article like this be sure that all terms in it are defined. What the heck is “W/m2″? Otherwise, it is good article and will surely draw the professional anti-AGW bloggers like flies to honey.

  3. Speedy says:

    No matter how hard I try, I can’t bring my self to feel sorry for someone who doesn’t get Watt per square meter.

  4. David B. Benson says:

    W/m2 is shorthand for Watts per square meter.

  5. Earl Killian says:

    paulm, check out figure S2 of Hansen’s Target Atmospheric CO2: Where Should Humanity Aim?: the orbital mechanics (Milankovitch cycles) that trigger ice ages aren’t set to do much soon. Global warming arrives at a relatively steady state for the next few thousand years. However, I feel “runaway” is the wrong word to use. If 1500±500 ppm 50 million years ago didn’t turn Earth into Venus, then 900 ppm soon is unlikely to do so. It will be quite unpleasant for humans, but “runaway” is probably the wrong word. After all, once the 1000 Gt of the permafrost is gone, that feedback dies down. According to ORNL, “1 ppm by volume of atmosphere CO2 = 2.13 Gt C”

    In the 16 June 2006 issue of Science, Zimov et. al had a little item “Permafrost and the Global Carbon Budget”. Here is a quote from that:

    “Using an overall average carbon concentration for yedoma of ~2.6%, as well as the typical bulk density, average thickness, and icewedge content of the yedoma, we estimate the carbon reservoir in frozen yedoma to be ~500 Gt (2). Another ~400 Gt of carbon are contained in nonyedoma permafrost (excluding peatlands) (3), and 50 to 70 Gt reside in the peatbogs of western Siberia (4). These preliminary estimates indicate that permafrost is a large carbon reservoir, intermediate in size between those of vegetation and soils. Our laboratory incubations and field experiments show that the organic matter in yedoma decomposes quickly when thawed, resulting in respiration rates of initially 10 to 40 g of carbon per m^3 per day, and then 0.5 to 5 g of carbon per m^3 per day over several years. These rates are similar to those of productive northern grassland soils. If these rates are sustained in the long term, as field observations suggest, then most carbon in recently thawed yedoma will be released within a century–a striking contrast to the preservation of carbon for tens of thousands of years when frozen in permafrost.”

  6. Shannon says:

    “If we are entering a negative PDO, that could slow the rate of global warming” implies causality when you earlier quoted JPL that this is unknown.

  7. David B. Benson says:

    “If we are entering a negative PDO, that could slow the rate of global warming” is, in the long run, false.

  8. Graeme Bird says:

    The globe isn’t warming. The planet is cooling. We know this from the Argos floats. You ought not be spreading inaccurate propaganda and lies.

  9. Graeme Bird says:

    We are in no way likely to get record temperatures in the 2010’s. In fact this is borderline impossible. And by the 2030’s we will have very cold temperatures indeed.

    Your analysis appears to be static. As if all changes are registered instantaneously.

    [JR: Your analysis appears to be disinformation. But I’d be happy to take a bet with you that the 2010s will be the warmest decade in the historical record.]

  10. David B. Benson says:

    Graeme Bird wrote “You ought not be spreading inaccurate propaganda and lies.” That’s right. You shouldn’t.

    Here are the 5 year averages of the HadCRUTv3 global temperature product:

    http://tamino.files.wordpress.com/2007/12/5yrave.jpg

    Those are the surface temperatures. You know, where we live? See any recent cooling?

    I thought not…

  11. Jay Alt says:

    Badgersouth asks:
    what the heck is W/m2?

    Watts/sq. meter.
    Here is a chart from IPCC sources showing different processes to the earth’s energy balance. (Negative => cooling while positive => warming.) Joe points out the small effect of solar irradiance (next to last) compared to human contributions (last line).

    http://img444.imageshack.us/img444/9894/radiativeforcingpb3.png

  12. Graeme Bird says:

    Okay lets go over it again. The globe is cooling. If tamino says otherwise tamino is a fraud. The globe is cooling. The Argos floats have spoken.

  13. Graeme Bird says:

    Ha Ha Good one. You chose a graph where the fact that the globe is cooling would of course be obscured.

  14. Tom G says:

    Personally I’m getting sick and tired of the planet is cooling bs.
    If the planet is cooling, why is all the bloody ice melting?

  15. Joseph says:

    I’m new to the temperature and related data, but I’ve analyzed it, and I’m a bit concerned. First, it doesn’t look like it is generally known what the equilibrium temperature should be given current levels of CO2. Calculations based on physics equations probably underestimate. I doubt it’s 1 degree (C). So we’re probably working our way up to a pretty high temperature value, regardless of whether CO2 concentration continues to increase. We’d have to decrease CO2 concentration pretty drastically to minimize the end result.

  16. paulm says:

    Joseph, You have a great site. I look forward to new posts.

    As I couldnt post a comment on your blog here is a comment on ….
    Hurricanes and Temperature are Indeed Associated

    The storm frequency seems to lag temp slightly and there appears to be a gentle fit on the sinusoidal average that visually seems to run through both graphs.

  17. Official stats on global sea ice extent here:

    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg

    The ice is not melting and the sky is not falling. There is no significant overall trend as there is increased ice cover in the south and decreased in the north, but all of this is very seasonal. It’s too early to say at this stage if there is a cooling trend. Seems everyone here has already made up their minds. We’ll see what the data tells us in a year or two from now.

  18. John Hartz says:

    Will Nitschke: The graph that you have referenced addresses just two dimensions of sea ice, i.e., witdth and breadth. It does not address the third dimension, i.e., depth. For comprehensive and up-to-date analyses of sea ice, go to the website of the The National Snow and Ice Data Center at: http://nsidc.org/

  19. Graeme Bird says:

    “Personally I’m getting sick and tired of the planet is cooling bs….”
    If the planet is cooling, why is all the bloody ice melting?”

    Well you are going to have to get over your tiredness. Because thats what is happening.

    [JR: Rest of post deleted. We try to deal in citable, scientific sources here. Not disinformation.]

  20. John Hollenberg says:

    > Okay lets go over it again. The globe is cooling. If tamino says otherwise tamino is a fraud. The globe is cooling.

    Joe, is there some reason to allow this debunked nonsense to be posted here?

    [JR: My apologies. I spent the day writing, not reading comments. Silly me!]

  21. paulm says:

    Can I suggest that we point nonbelievers (deniers) to Joseph’s original post on this post ( comments should be read) .

    http://autismnaturalvariation.blogspot.com/2008/06/anthropogenic-global-warming-is.html

    Here in a straightforward manner, he clearly and eloquently uses statics on raw data available to us all, to conclusively show the link between man made emissions of CO2 and temperature rise over the last century. It stops deniers in their tracks – as you can see from the following comments.

    On his new site to deal with the topic –
    ‘Residual Analysis – A closer look at scientific data and claims’

    http://residualanalysis.blogspot.com/

    (Hey Joe, Joseph needs some accolade and his site needs promotion)

    he clearly shows, using basic statistic to laypersons, how a number of climate change issues / trends are shown to be true to a very high confidence. The insurance industry should be interested in this. I am sure this analysis must have been done previously, if not – WOW. It certainly hasn’t been made readily available to the public, which it should, as it is very convincing.

  22. Joseph says:

    The storm frequency seems to lag temp slightly and there appears to be a gentle fit on the sinusoidal average that visually seems to run through both graphs.

    Yes; 1 year appears to be the best lag, but I don’t know what explains that. I thought that maybe including September, October and November in the year average amounted to including next year’s data in the current year. But it doesn’t look like that’s it.

  23. Joseph says:

    As I couldnt post a comment on your blog

    BTW, I just noticed I was requiring a Blogger account to post, which was unintentional. It’s fixed.

  24. Joseph says:

    For anyone interested, I posted a follow-up of the temperature vs. named storms analysis. Look for the graph there. This is actually a much simpler and obvious way to illustrate the association.