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Climate change on Mars

Posted on 13 March 2008 by John Cook

Global warming on Mars is a popular skeptic argument, even invoked by presidential hopeful Fred Thompson (I'm sure it had nothing to do with his failed campaign). The argument goes that Mars is warming at the same time and at a similar rate to Earth. Therefore global warming on both planets must have the same cause (eg - the sun). To determine whether this argument is valid, we need to examine the evidence that Mars is warming and what drives Martian climate.

Empirical evidence for Martian global warming

The primary empirical evidence for long term, global warming on Mars comes from Fenton 2007. Fenton compared a composite snapshot of Mars from 1977 taken by the Voyager spacecraft to a 1999 image compiled by the Mars Global Surveyor (referencing work from Geissler 2005). The 1977 snapshot showed a brighter planet. In 1999, the planet had a lower albedo, with prominent darker regions in the southern mid and high latitudes. Using the albedo changes in a general circulation model, Fenton calculated a 22 year global warming trend of 0.65°C.

Figure 1: Snapshots of Mars 1977 (top) and 1999 (bottom). Image courtesy of Geissler 2005.

Fenton attributed the warming to surface dust causing a change in the planet's albedo. Martian dust plays a major role in the planet's climate (Kahn 1992). Solar variations are not the main driver of Martian climate. Nevertheless, an important question remains: is the interpretation of long term global warming on Mars correct?

A broader view of Martian climate change

To put these results in proper perspective, an understanding of what drives Martian climate is required. Global dust storms increase the surface albedo by settling brighter dust on dark surfaces. Within a year after a dust storm, various wind systems remove the dust and Mars returns to a normal, lower albedo.

The 1977 snapshot was taken after a global dust storm had deposited dust over the southern latitudes, lightening the planet surface. Before the storm, the planet had albedo comparable to recent measurements (Szwast 2006).

Fenton drew conclusions about long term climate by comparing two end points. This led to the classic error of mistaking weather for climate (similar to the recent global cooling argument). When you look at the broader data, there is no discernable long term trend in albedo:

Figure 2: Comparison of data sampling by Fenton 2007 (left, comparing 2 end points) and the full sample of data (courtesy Mark Richardson).

The apparent long-term warming between the 1970's and 1990's is largely a consequence of the timing of the two snapshots used. The "brighter" 1977 snapshot was immediately after a global dust storm when the planet was temporarily lighter. The "darker" 1999 snapshot was of the planet in it's usual state. There is little evidence that Mars is undergoing decadal-scale, long term global warming. In fact, following the 2001 global dust storm, the southern hemisphere was brighter than in 1977 (Szwast 2006).


The empirical evidence isn't conclusive on whether global warming is happening on Mars. However, to answer the question on whether the sun is causing Earth's global warming, there is plentiful data on solar activity and Earth's climate. Many papers have examined this data, concluding the correlation between sun and climate ended in the 70's when the modern global warming trend began.

So the argument that Martian warming disproves anthropogenic global warming fails on two points - there is little empirical evidence that Mars is warming and Mars' climate is primarily driven by dust and albedo, not solar variations.

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Comments 1 to 22:

  1. Re: "the correlation between sun and climate ended in the 70's when the modern global warming trend began." is only true if the factoring is incomplete. See my last comment on "Global cooling: the new kid on the block". Richard Mackey has developed his hypothesis based on the earlier work done by Rhodes Fairbridge.
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    Response: Fairbridge's work addresses the cause of solar variations (eg - planet alignment affecting the sun's angular velocity which affects solar output). Regardless of what's causing solar variations, we have empirical measurements of solar output. And many studies comparing solar output and global temperatures have concluded the sun's role in global warming is minimal.
  2. Yes and many have concluded the opposite. Your argument is stretching the claim that TSI is down since 1975. I don't know, I don't read many papers in solar astronomy, however asking around the astronomy professors I work with I can't find any that agree with the contention that TSI has been dropping since 1975. The few who were involved in solar astronomy looked at me like I was crazy when I suggested it. Maybe your reference on correlation between sun and climate ending in 1975 isn't all that good. I actually don't think the Mars warming is necessairily related to Earth warming. But the idea that the Sun is cooling through this recent warming is just wrong.
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    Response: I've never said the sun was cooling, just that the correlation between sun and climate ended in the 1970's. There are several composites of TSI which show slightly different trends over the last 30 years. However, the fact that scientists are arguing over whether the sun is showing a slight upwards trend or a slight downwards trend or if there's even a trend at all only serves to underscore the sharp divergence between sun and sharply rising temperatures.
  3. The graph you posted on the "it's the sun" thread showed a drop after 1975 while the actual case appears to be a slow increase generally up until about 2003. I think what is really bothering me is that you appear to think the correlation must be linear and not involve a lag time, while not holding CO2-climate relation to anything like a similar standard Is the correlation CO2-climate better than the sun-climate correlation for the last century? I think you would have to admit it isn't. You have to choose a very specific time interval, something like, longer than 20 years shorter than 50 years or the CO2-climate correlation loses the comparison. Another trouble is the "sharply rising temperatures" are they? Isn't that contention already 10 years out of date? If temperature doesn't have to keep lock step with CO2 why do you think it should keep lock step with TSI or the hypothesis fails. Shouldn't you hold both hypothesis to the same standard? I am not even disagreeing here on your main point it just seems that you have a double standard. Maybe we can't avoid it when personal beliefs intrude.
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    Response: As there are a number of forcings that influence climate, CO2 doesn't always correlate perfectly with climate. For example, right now we're experiencing cooling because La Nina is temporarily overpowering long term warming. On a more long term scale, mid-century cooling occured while CO2 levels were rising because cooling from rising aerosol levels temporarily overpowered CO2 warming.

    Now if I argued CO2 was the driving force for mid-century cooling when the data clearly shows a break down in correlation, I would be mistaken. Instead, the obvious conclusion is that some other forcing/s was driving the cooling. Similarly, we cannot conclude the sun is driving current warming because the correlation has broken down. Therefore some other forcing/s must be the driving force of the last 3 decades of warming.

    The breakdown in correlation between sun and climate doesn't prove CO2 warming. It just disproves the argument that the sun is the main driver of global warming.
  4. Re#3: Shouldn't the stratosphere have warmed if the sun was the source? I believe the data show a cooling stratosphere.
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  5. May I draw your attention to: "Scientists Verify Predictive Model For Winter Weather" - - and "Warm Winter Predicted For United States" - - and "Coolest Winter Since 2001 For U.S., Globe, According To NOAA Data" - - So much for climate model accuracy.
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    Response: In Oct 2007, the NOAA predicted a winter that was warmer than the long term average but a "cooler winter than last year". It also predicted a moderate-to-weak La Niña was likely to persist through the winter. What actually happened was the winter was still warmer than the long term average but cooler than expected due to La Niña being stronger than expected (moderate-to-strong). Short term internal variability is always harder to predict due to the chaotic nature of weather. Which is why climate prediction averages out the chaotic noise of weather to deduce long term trends.
  6. A couple of points: 1) The warming on earth is least at the south pole, and so it seems least also on mars south pole. If there is a correlation then mars should be colder this winter as well (just like the earth). 2) I have been comparing daily temperatures to record temperatures for the North East U.S. this winter and not only is it colder than recent years, it's been running about 10 degrees F colder than long term averages. I don't have access to global data but I know that everywhere other than parts of europe has had a miserable winter.
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  7. By the way, Mackey predicted that when artic ice had melted enough that asia would have one hell of a winter.
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  8. Looks like NOAA had a not so good prediction; average temperatures that ran about 10 degrees F colder than last year were the rule not the exception. I don't think you have disproven the sun being the main driver any more than the mid century cooling disproved CO2 as the main driver; the situations are clearly similar. The fact that you have another hypothesis that allows you to say CO2 as a driver is not disproven because it cooled from 1940-1970, does not mean there is not also a secondary affect that is masking solar affect from 1975-1998. (like a simple time lag) Even if, as you claim, the sun/climate correlation is broken. This is a further example of a double standard.
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  9. Quietman point #1 in post 6 seems to make no sense. Mars winters and summers are of very different durations than Earth'and are not resonant. Furthermore, the planet's axis and orbit lead to naturally warmer south pole summers on Mars:
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  10. Philippe Please note that I said "If there is a correlation". Regardless of the difference in axial tilt, IF it's solar warming we should see some correlation, making some allowance for La Nina of course. I have not heard any further information on what Mars is doing so I am only speculating that IF it is solar activity then it should affect Mars in similar fashion to earth. When I said "this winter" I should have said "at this time". The cooler south pole remark was just a curious observation. Thanks for the Link.
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  11. The lack of correlation between Mars and Earth' climates is well known to Mars enthusiasts. Dust storms and warm conditions prevailed at the time of the Viking landings in the 70's, while Earth was entering the recent global warming trend we know. Then, while Earth was warming, Mars cooled down, only to experience dust storms and warming again in the recent past. To my knowledge, there is no significant correlation with solar activity either. It is rather ironic that some skeptics will go at length on how Earth has not warmed since 1998 and then go on to attempt correlations with Mars, which did warm significantly since 1998. I have looked at a variety of claims about other planets' "climates" and so far nothing even remotely convincing has surfaced.
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  12. Philippe You are right of course in that there is no correlation between Mas's climate and Earth's. That is not what I was trying to point out. The Earth has oceans, cloud cover and thicker atmosphere just to name a few. What I am attempting to point out is that the suns effect on one planet should be reflected by a similar effect on another. If there is no effect then we can rule out TSI. This has nothing to do with skepticism, it was only meant to be an observation. Since you appear to know more about Mars, maybe you could explain why this observation is false?
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  13. You answer your own question when you say that there is no correlation. As I said, as Mars was cooling down, the Earth was warming, then Earth was warming as Mars remained cool, then Mars was warming again as Earth's warming appeared to slow down, although that slowing is most likely statistical noise.
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  14. Mars should have, theoretically, a higher sensibility to solar activity as the earth because that planet is red. Since most solar irridiance is in de UV-part of the spectrum which it's not reflected by the Martian surface. The colour 'red' means that it longer wavelengths reflects and short wavelengths absorps.
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  15. It appears these guys wouldn't agree; Over 400 Prominent Scientists Disputed Man-Made Global Warming Claims in 2007 Senate Report Debunks "Consensus" December 20, 2007 AND just for the record, Fred Thompson didn't run a "failed"'s why; How the Republican Party Committed National Suicide By JB Williams Who Hijacked the Primaries? by Brett Winterble The Death of Conservatism? 43 Mistakes and the GOP's Dobson's Choice GOP Leads Astray Conservative Blackout by Lisa Fabrizio AP Gives Thompson the ‘04 Treatment by Jed Babbin
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  16. Victor Actually as I understand it, Mars should be less sensitive because it lacks the magnetic field that protects the earth. The sun distorts the magnetic field of the earth, altering what radiation can pass through but since mars lacks this field the sun has no martian field to distort so its effect is much the same all the time. I am sure Philippe will correct me if I got it wrong. :)
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  17. Quietman: planetary magnetic fields shield planets from particles (solar winds), not from solar irradiance.
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  18. Philippe So what you are saying is that the same forces that cause the increased speed of the solar wind do not carry along with it the increased heat that is expelled in the microflare?
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  19. I suggest that people who think that the sun is responsible, and cite warming on other planets become familiar with the Inverse Square Law. ;)
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  20. Problably wrongly, but I had the impression that this website was sort of impartial in assesment. But not mentioning in this thread the real reason why some people started to associate the two events, which is: THE SHRINKAGE OF HE MARTIAN NORTH POLE, really takes me aback. Does any one knows how that is going? -- for years, since mid 90 I've read that Mars pole was diminishing: Does anybody knows how that is now? Is it following the sun and started do grow again or not?!
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  21. Olympus Mons, I did some of your work for you: Excerpt:"Seasons are of unequal length. Mars is closest to the Sun in southern summer/ northern winter, and furthest in southern winter/northern summer. The southern hemisphere has shorter, warmer summers and longer, colder winters. During southern summer, dust storms often circle the entire planet." Which brings us back to this article: Outstanding pics on this presentation: More info here:
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  22. Quietman, seems you have left the Arctic ice thread, where I was asking you about this comment here on the solar wind. I don't understand what you're trying to say and I don't see anything in the article you link that clarifies it. How does the solar wind "carry" heat? What is your definition of heat? How do you think that heat is normally transmitted through space? What references do you have that particles winds participate in the Earth' energy budget?
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