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Global warming on Mars, ice caps melting

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The skeptic argument...

Mars is warming

"Scientists are telling us Mars is experiencing its own planetary warming. NASA says the Martian South Pole's ice cap has been shrinking for three summers in a row. Maybe Mars got its fever from earth. If so, I guess Jupiter's caught the same cold, because it's warming up too, like Pluto. I wonder what all those planets, dwarf planets and moons in our SOLAR system have in common. Hmmmm. Solar?" (Fred Thompson).

What the science says...

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Mars is not warming globally.

It is hard to understand how anyone could claim global warming is happening on Mars when we can’t even agree what’s happening on the planet we live on. Yet they do, and the alleged reasoning is this; if other planets are warming up, then there is some solar system-wide phenomena at work – and therefore that it isn’t human activity causing climate change here on Earth.

The broadest counter argument depends on a simple premise: we know so little about Mars that it's impossible to say what trends in climate the planet is experiencing, or why changes occur. We do have information from various orbiting missions and the few lander explorations to date, yet even this small amount of data has been misunderstood, in terms of causal complexity and significance.

There are a few basic points about the climate on Mars that are worth reviewing:

Planets do not orbit the sun in perfect circles, sometimes they are slightly closer to the sun, sometimes further away. This is called orbital eccentricity and it contributes far greater changes to Martian climate than to that of the Earth because variations in Mars' orbit are five times greater than the Earth.
Mars has no oceans and only a very thin atmosphere, which means there is very little thermal inertia – the climate is much more susceptible to change caused by external influences.
The whole planet is subject to massive dust storms, and these have many causal effects on the planet’s climate, very little of which we understand yet.
We have virtually no historical data about the climate of Mars prior to the 1970s, except for drawings (and latterly, photographs) that reveal changes in gross surface features (i.e. features that can be seen from Earth through telescopes). It is not possible to tell if current observations reveal frequent or infrequent events, trends or outliers.

A picture is worth a thousand words, but only if you understand what it is saying

The global warming argument was strongly influenced by a paper written by a team led by NASA scientist Lori Fenton, who observed that changes in albedo – the property of light surfaces to reflect sunlight e.g. ice and snow – were shown when comparing 1977pictures of the Martian surface taken by the Viking spacecraft, to a 1999 image compiled by the Mars Global Surveyor. The pictures revealed that in 1977 the surface was brighter than in 1999, and from this Fenton used a general circulation model to suggest that between 1977 and 1999 the planet had experienced a warming trend of 0.65 degrees C. Fenton attributed the warming to surface dust causing a change in the planet's albedo.

Unfortunately, Fenton’s conclusions were undermined by the failure to distinguish between climate (trends) and weather (single events). Taking two end points – pictures from 1977 and 1999 – did not reveal any kind of trend, merely the weather on two specific Martian days. Without the intervening data – which was not available – it is impossible to say whether there was a trend in albedo reduction, or what part the prodigious dust storms played in the intervening period between the first and second photographs. Indeed, when you look at all the available data – sparse though it is – there is no discernable long term trend in albedo.

At this time, there is little empirical evidence that Mars is warming. Mars' climate is primarily driven by dust and albedo, not solar variations, and we know the sun is not heating up all the planets in our solar system because we can accurately measure the sun’s output here on Earth.

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Planet wide dust storm

A good example of how dust affects Mars climate: over 2007, Mars suffered a titanic dust storm that engulfed the entire planet. The dust storm contributed to a temporary warming effect around Mars, raising the temperature of the atmosphere by around 20-30°C. Interestingly, whereas the atmosphere of the planet heats up, the surface of the planet cools down because it receives much less solar heat.

Acknowledgements

Many thanks to Mark Richardson for his advice and materials on Martian climate. Thanks also to Jon for the heads-up on Mark Richardson's latest AGU presentation.

Further viewing

Comments

Comments 1 to 20:

papertiger at 10:20 AM on 16 September, 2007
Sediment cycles on Mars in resonance with Earth

After computation of the astronomical Milankovitch cycles on deep sea cores for the last 2.4 Ma the same cycles revealed to exist in land sediment series: Long Term (last 2.4 Ma, Pleistocene) and Middle Term (last 127Ka, Last Interglacial - Last Glacial Time-span) Time Series after cycle computation with the newly developed ExSpect method. Moreover, the same calculation method proved useful for Short Term Time Series as well on sediments of the last 10.000 years (10Ka). The latter cycles as those obtained for ice and glacial lake deposits on Mars could also clearly be traced back in the planetary correlations computed by the NASA Goddard Space Flight Center. This points to an extra terrestrial astronomical forcing of the origin of all these cycles on both planets Earth and Mars.

Which begs the next question - how would they know this without taking a sediment sample on Mars?
Answer: they got one with the the Mars orbital satellite.
papertiger at 10:23 AM on 16 September, 2007
Nice picture of the southern icecap by the way.
Response: Thanks, it was either a photo of the icecaps or a picture of Fred Thompson. I think I made the right choice.
Philippe Chantreau at 02:36 AM on 24 September, 2007
Once again, it is useful to ask ourselves this question about other planets: how unusual is this (the recent southern ice caps sublimation)? This link gives a hint: http://www.msss.com/http/ps/seasons/seasons.html. Consider also that Mars' orbit takes about 589 days, letting us observe only three full seasonal cycles in 5 years.

It has long been known that Milankovitch cycles are the best fit to the available evidence for historic glaciation-deglaciation cycles on Earth. The energy source, the Sun, is extra-terrestrial but there is no evidence that it got brighter or dimmer in proportions apt at changing our climate and in any case, that is not what Milankovitch cycles are. As far as I can recall, the energy received changes because of the planet getting closer, farther, or being oriented slightly different, which is a function of its orbit and precession; in that sense, extra-terrestrial is a little misleading, since these qualities could really be called intrinsic to the planet.

The point of the paper cited by papertiger is that Earth and Mars' Milankovitch Cycles could be resonant. I wonder if anyone has tried to obtain some level of confirmation from pure celestial mechanics calculation. In any case, it is interesting but quite irrelevant to the current terrestrial warming, which does not correlate well with neither Milankovitch nor with the so-called Martian warming. That Martian warming is really a re-warming back to the kind of weather seen by the Viking crafts, and the Earth should now be heading for cooler climate if only Milankovitch was at play.
Philippe Chantreau at 02:55 AM on 24 September, 2007
This seems to be the best work so far on Mars' recent weather: Global warming and climate forcing by recent albedo changes on Mars
Response: Thanks, this was the study I was refering to but I didn't have a direct link to the study. I've updated the page with the link added.
StanislavLem at 13:52 PM on 14 November, 2007
Sunspot numbers are extremely crude indicator of solar activity and do not encompass many other manifestations of it (sorry adding the F10.7cm Radio Flux Index also won't do the trick). So repeating the argument that sunspot numbers have leveled out since 1950 doesn't necesseraly mean what you want it to mean (no additional inputs from the Sun in the Earth's or any other planet's climate). Also, focusing only on the total solar irradiance (TSI) as the only possible way in which solar activity influences Earth type planets' climates is just selective presenting/lack of knowledge (I hope it is the second, since the first would imply very bad things about your presentation of facts).

In fact, there some quite viable hypothesis that explain how non-TSI manifestations of solar activity cause dust storms on Mars (by the way those are possible for the Earth as well). Obviously there is still to little data to confirm or reject them. By don't "get rid of" Mars just yet. Mars is actually quite good "test case" for the anthropogenic vs. natural warming debate. As a planet it is quite similar to the Earth in many important aspects and it is as close as ti the Earth as it gets in the solar system. Some of the main advantages for a possible "Mars test case" are: 1. There is no human activity there to influence the Marsian climate in any way, so we can discount that factor 2. there is no ocean to provide huge termal inertia, so solar effects will be much more immediate, 3. Marsian day is almost identical to Earth's day, 4. Marsian atmosphere is similar Earth's mid upper atmosphere, so this simplifies estimation of the solar effects quite a bit.

The geometrical effects that you mention (orbit's eccentricity, axis tilt) are quite easy to correct for, much easier that cloud structure in the current climates for example.
John Cross at 04:41 AM on 16 November, 2007
StanislavLem: An interesting post, but even better for me is that it lets me play skeptic for a change ;-) .

You do not specify what viable hypothesis explain how non-TSI manifestations of solar activity cause dust storms on Mars, so I can not address that, but I do not agree with your idea that the Martian atmosphere is a good test bed to allow observation of the effect of human activity. Off the top of my head, here are 4 major differences and, in my opinion, each one is enough to invalidate such a comparison without a large amount of research (i.e. several continuous martian weather stations).

1) No magnetosphere so there is a direct ionization of atmospheric particles.

2) I would disagree with your comparison about pressure. If you are looking at total atmospheric pressure, then Mars is more like the stratosphere. If you are talking about partial pressure of CO2, then the surface of Earth is the best we can get, but that is even too low. In any case, both of these do not produce some of the more important effects such as pressure broadening of the CO2 absorption spectrum.

3) There is no water to speak of and thus the vertical thermal transport associated with water does not exist.

4) Finally, the drivers also seem to be much different. Dust storms are a key part of the Martian climate as are sublimation winds from the poles. These have no equivalent on earth.

Regards,
John
Will Nitschke (www.capitaloffice.com.au) at 10:32 AM on 19 December, 2007
You wrote:

"Mars has one of the highest orbital eccentricities of any planet in our solar system which causes much greater seasonal changes than on Earth."

OK, but has the orbit of Mars changed in the last 30 years or the last 100 years to explain the extra warming? If the answer is 'yes' can you explain why and how? If the answer is 'no' then doesn't that point to an extra-planetary explanation? It seems in your article you begin by ruling out the sun, then suggest you're going to offer alternate explanations, then fail to do so. Yes the storms can cause the warming, but what is causing the extra turbulence in the atmosphere leading to the storms?
Response: The orbit wouldn't have changed over a 30 year or 100 year period - orbital changes occur over much longer periods. By orbital eccentricity, I mean Mars' orbit is more elliptical than Earth's which is more circular. This means Mars's distance from the sun changes more dramatically through a Martian year which means its seasonal changes are more dramatic than Earth's. I thought the alternate explanation was clearly explained - dust storms reducing the planet's albedo.
Will Nitschke (www.capitaloffice.com.au) at 12:38 PM on 19 December, 2007
Thanks for the response, but it appears you only want to take the argument up to a fixed point. What's caused the *increase* in dust storms that is leading to higher temperatures? Obviously not the more elliptical orbit of Mars alone as this hasn't changed. Which only leaves an extra-planetary explanation, doesn't it? Your explanation only makes sense if the temperature of Mars was not showing a trend increase. Storm activity would therefore be relatively consistent over time and the temperature on Mars would be relatively consistent over time. But it isn't. If this is wrong (which is quite possible of course), you need to explain how these storm cycles can last decades and lead to decades of warming, and then presumably afterwards, decades of cooling, only by means of interactions within the Martian atmosphere itself.
GMB at 19:07 PM on 27 December, 2007
If Jupiter, the earth, Mars, Pluto and so forth are warming... then its the sun. These alternative feeble excuses are really clutching at straws.
Wondering Aloud at 09:13 AM on 4 January, 2008
I haven't seen anything on Jupiter system as a whole that would convince me it is warming to any significant extent, and Pluto is likely caused by orbital eccentricity it has been closer than average to the sun in recent years
Philippe Chantreau at 14:01 PM on 15 January, 2008
Mars cooled down signficantly between the Viking landings and the recent "warming" trend, while Earth was consistently warming throughout that time, making the correlation highly doubtful.

Pluto has not been observed through a complete orbit yet, arguing about its "climate" is pointless. The observations match expectations from its seasonal cycle and the albedo changes seen since the 50s (likely due to collection of space materials). Furthermore, if the Sun could really throw out the energy to affect Pluto so much, we would be frying.

There is no convincing evidence that Jupiter's "climate" (once again more a figure of speech than a observed reality) is prone to be affected by variations in TSI so minute that we had to have satellites around Earth to actually mesure them.

Among the inner planets, Venus, most likely to show changes due to its proximity to the Sun and huge greenhouse effect is not showing any warming.
Quietman at 10:50 AM on 12 March, 2008
It's not just Mars. Ever read the papers by the late Dr. Rhodes Fairbridge?
Philippe Chantreau at 13:04 PM on 11 September, 2008
Re-reading through this, I thought it would be worth pointing to a detail mentioned by Stanislav Lev. Mars is not really the closes planet to Earth. Although Mars happens to be very close at times, in average, Venus is closer.
harmonyfuture at 10:56 AM on 12 March, 2009
If anyone visits again, could any comment be made on possible chemical reactions resultant from storm activity on the surface. Excuse ignorance, ignore if stupid. Thanks
SaganGathering at 18:59 PM on 25 February, 2010
I'm not going to address the data directly just now, because there's another problem with the "other planets are warming" argument. Here it is.

We have a handful of probes on Mars and an orbiter. Mars is the planet we probably know the most about besides Earth. And even with that equipment we can only get the faintest idea of what's going on with the temps there on Mars. Or other planets for that matter.

We have laughably few samples of temps on other planets as compared to the astounding array of data on our own Earthly climate trends.

It's absurd to claim with any confidence that we know for certain that other planets or moons are warming or cooling, when we have relatively little data about them -- all the while ignoring our vast armada of land and sea-based temperature probes right here on Earth (not to mention orbiting satellites).

Should we dismiss the data we have on our own planet's temperature trends because of a smattering of temperature measurements on any other planet? Which data-set do you think would be more reliable? The one we have here at home, of course. Because we have many, many more sources and samples, and over a longer period of time.

We know far more about the temperature trends on our own planet than on any other planet, and yet certain people use highly questionable speculations about other planets' temperatures to try to dismiss the dta trends we see here at home.

To use this data (or records from other planets) as reliable evidence of anything more solid than the temperature sampling we have for Earth, is on its face absurd.

I would also like to say that there's too much attention paid to Earthly CO2 alone. Methane and Nitrous Oxides may be at least as problematic. Most of this comes from livestock production. Certainly, getting them under control first will give us more return on investment, and quicker too.
ReBar at 06:18 AM on 9 March, 2010
Someone must have the answer to why dust from volcanos and pollution cause cooling on earth and warming on Mars.
Ned at 09:21 AM on 9 March, 2010
ReBar writes: Someone must have the answer to why dust from volcanos and pollution cause cooling on earth and warming on Mars.

Read the article again. Lots of dust (in 1977) made Mars slightly cooler, and less dust (in 1999) made the planet slightly warmer. On both Earth and Mars, more dust = cooler.

I hope this helps.
acerj at 15:19 PM on 24 March, 2010
Actually Sagan, temp measures on other planets could be considered more reliable than some I've seen taken on earth. You are showing an obvious bias. If we are concerned with finding the truth why not look at other planets.
Ned at 20:42 PM on 24 March, 2010
Actually Sagan, temp measures on other planets could be considered more reliable than some I've seen taken on earth.

On Earth we have buoys, drifters, and satellites measuring the temperature of the oceans; met stations and satellites measuring the temperature of the land surface; boreholes measuring temperatures beneath the surface; and satellites and balloons measuring temperatures in the atmosphere.

That's orders of magnitude more information than we have about temperatures on any other planet.
papertiger at 11:50 AM on 31 July, 2010
I notice that the link to the ice core on Mars from comment 1 is defunct, so here's another.
Same picture, a bit more stylishly presented.

It shocks me that after close to three years, numerous rewrites, you still haven't come close to refuting my original comment.