Arguments
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).
Conclusion
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.
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.
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.
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.
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.
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.
http://www.exploringmars.com/science/seasons.html
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.
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.
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?
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.
Over 400 Prominent Scientists Disputed Man-Made Global Warming Claims in 2007
Senate Report Debunks "Consensus" December 20, 2007
http://epw.senate.gov/public/index.cfm?FuseAction=Minority.SenateReport
AND just for the record, Fred Thompson didn't run a "failed" campaign...here's why;
How the Republican Party Committed National Suicide By JB Williams
http://www.michnews.com/artman/publish/article_19227.shtml
Who Hijacked the Primaries? by Brett Winterble
http://www.humanevents.com/article.php?id=24726
The Death of Conservatism? 43 Mistakes and the GOP's Dobson's Choice
http://www.freerepublic.com/focus/f-news/1961546/posts
GOP Leads Astray
http://gopleadsastray.blogspot.com/
Conservative Blackout by Lisa Fabrizio
http://www.spectator.org/dsp_article.asp?art_id=12517
AP Gives Thompson the ‘04 Treatment by Jed Babbin
http://www.humanevents.com/article.php?id=24127
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. :)
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?
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?!
http://www.uapress.arizona.edu/onlinebks/mars/chap04.htm
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:
http://www.nature.com/nature/journal/v446/n7136/abs/nature05718.html
Outstanding pics on this presentation:
http://cpt.phys.utk.edu/~th/Astro151/Lecture12.pdf
More info here:
http://www.msss.com/http/ps/seasons/seasons.html.
http://www.uapress.arizona.edu/onlinebks/mars/chap04.htm
http://www.sciencemag.org/cgi/content/abstract/228/4704/1160
http://www.sciencemag.org/cgi/content/abstract/228/4704/1160
http://www.sciencemag.org/cgi/content/abstract/228/4704/1160