The Warming Mars

Since the canard that since Mars is warming anthropogenic warming here on earth must be false pops up again and again (like in whack-a-mole), I think it appropriate to post something about it.

The only thing possibly linking a warming on Earth and Mars (if there were a common cause) is variations of the sun’s radiation. This hasn’t changed much in at least the last 30 years, apart from the 11year solar cycle:

It is clearly visible that even those cyclic changes are small – about 1 W/m2. To compare with forcings by the greenhouse effect, this has to divided by four, because the 1367 W/m2 apply only to a surface perpendicular to the direction of the sun (like at the equator without absorption by the atmosphere), while forcings are calculated for the whole surface of the earth. The greenhouse forcings (the additional effect by manmade GHGs) are at about 1.5 W/m2. Compare this with 0.25 – and it is irrelevant anyway, because these changes go up and down.

Moreover, in the last few years, it has gone down, not up. But we just observed the warming on Mars in just those last few years.

Now there is a new paper (for those fortunate enough to have a subscription) published in Nature that explains the warming trend on Mars with changes in the albedo. It is cited in Scientific American:

Snapshots over the past three decades have shown vast regions of the Red Planet’s surface have brightened or darkened by 10 percent or more, reflecting about 20 percent of incoming sunlight in total. To determine if albedo (reflectivity) changes affect the climate, researchers compared Viking orbiter photos from 1976 to 1978, which mapped the planet’s bright and dark spots, to those from 1999 to 2000, when the Mars Global Surveyor discovered a darker Mars.

See also this post by William M. Connolley.

Changes in albedo can have an effect. I have a small C program that calculates the expected temperature with

T = pow((solconst/(d * d))/(4*SIGMA)*(1.0 - albedo), 0.25);

With the values d (distance) = 1.53 AU, solconst = 1367 W/m2 (at 1 AU), SIGMA = 5.6704×10−8 (metric), and albedo = 0.16 the temperature gets 215.65K (-57.5C). With just 1 percent point increase in albedo (0.17) it gets 215.00K (-58.14C). We disregard the greenhouse effect on Mars here – which is there, but small (the average temperature on Mars is about 10 degrees higher).



Filed under global warming, science

10 responses to “The Warming Mars

  1. The key to the entire global warming discussion is not to take sides, but simply to integrate ALL incoming data into the underlying models. For example, Mars warming/cooling is an interesting apparent anomaly, and the discussion here gives important information, but does not give any cause for the change in albedo. Obviously, this matters. Until a good explanation appears, everyone should be careful about making claims one way or the other – the fact of what is happening cannot simply be ignored or discounted.

  2. Regarding the effect of the 11-year sunspot cycle, consider this: The increased solar flux is partially captured by our magnetic field, which partially shields us from incoming cosmic radiation, which has been absolutely demonstrated to be a significant cause of cloud formation. More solar flux equates to increasing atmospheric temperature, every 11 years. Add to this a well recognized 1,500 cycle of solar variation, and you are a long way toward producing the amount of warming we see right now.

    This may not be the answer, but it makes no sense to ignore this, while insisting that human activities cause the warming.

    One more point: The entire current increase in global temperature over about 100 years is about 1/2 deg. C. If you do the math, you will discover that – no matter the cause – drastic action simply is not caller for. We have plenty of time to consider what is happening, and to take appropriate measures, whatever they may turn out to be.

  3. Robert, my answer to your first comment:

    The articile in SciAm gives an explanation for the albedo changes:

    They found that the heat absorbed by dark rock kicks up winds that blow away shiny dust, leaving behind even darker rock.

    It further says that this happens after a season of dust storms in the 70s, which distributed the bright dust over the planet. So it looks like Mars is going through cycles of high dust storm activity which increase the albedo, followed by decreasing albedo by ‘dust cleaning’.

    But the cause is not that important. The fact that it is not solar radiation changes that cause a warming on Mars is. You may of course speculate that solar variability causes the albedo change, but then you have to explain the mechanism and why it makes Mars darker and not brighter, or indirectly, why it changes the dust storm behavior.

  4. Robert, answer to your second comment:

    I am not aware of an 11year cycle in global temperatures, but I will try to verify that.

    If cosmic rays were responsible for the warming (via the cloud effects), we would expect to observe a decrease in the cosmic ray flux in the last few decades. As far as I know, it has been observed that it did not change since the fifties. I will try to find the source, but I read it on realclimate.

    Thanks for your comments, btw.

  5. Okay, I found it: See this figure from this post on realclimate. The cosmic ray flux does not show any trend since the fifties. The 11 year cycle can be seen in the cosmic ray flux, but not in the temperature curve.

  6. Pingback: No correlation with Cosmic Rays « Fermi Paradox

  7. The simple fact is that solar varability accounts completely for observed warming, and will soon account completely for cooling that will peak about 2020. Check out this article for a good summary of what is actually appening:

  8. Pingback: Venus and all that « Fermi Paradox