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Global warming on Mars, ice caps melting

What the science says...

Select a level... Basic Intermediate
Martian climate is primarily driven by dust and albedo and there is little empirical evidence that Mars is showing long term warming.

Climate Myth...

Mars is warming
"Some people think that our planet is suffering from a fever.  Now scientists are telling us that Mars is experiencing its own planetary warming: Martian warming. It seems scientists have noticed recently that quite a few planets in our solar system seem to be heating up a bit, including Pluto. 

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."  (Fred Thompson).

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 Viking 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.

Last updated on 20 August 2010 by John Cook.

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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 42:

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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
  7. 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.
  8. 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.
  9. If Jupiter, the earth, Mars, Pluto and so forth are warming... then its the sun. These alternative feeble excuses are really clutching at straws.
  10. 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
  11. 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.
  12. It's not just Mars. Ever read the papers by the late Dr. Rhodes Fairbridge?
  13. 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.
  14. 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
  15. 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.
  16. Someone must have the answer to why dust from volcanos and pollution cause cooling on earth and warming on Mars.
  17. 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.
  18. 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.
  19. 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.
  20. 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.
  21. This comment is a response to a comment by Noel Edwards on a different, less appropriate, thread.

    Noel wrote
    Moderator I have read most of your references. They indicate that CO2 is capable of absorbing radiation at different frequencies. Already known. But there is nothing in those references that indicate why Mars is cooler than it should be when it has lots more CO2 than Earth. There are no other issues associated with Mars, other than it has some 14 times as much CO2 in its atmosphere than has planet earth. Its maximum temperature is the approximately the same as Earth's average temperature and its average temperature is the approximately the same as Earth's minimum temperature. The physics is similar.
    Noel, you are very, very incorrect, as dsleaton and Matthew pointed out to you.

    There is no basis for your claim that Mars "is several degrees C cooler than it otherwise should be." More details on why the water vapor feedback is so much smaller on Mars than on Earth are in David Archer's book "Global Warming: Understanding the Forecast", pages 71-72. If you don't want to buy the book or borrow it from your library, you can watch his class lectures for free.

    If you insist on details, here is just one of several examples of calculations that Mars should in fact be the temperature it is:
    Forget, et al. (1999).

    A general-reader-comprehensible overview of modeling the Martian atmosphere purportedly is provided by Stephen R. Lewis's article "Modelling the Martian Atmosphere, though all but the first page is behind a paywall.

    If you really, really, want to understand the difference between Mars and Earth, get ahold of this book when it comes out (probably December 2010); it will have a workbook and computer models you can run: "Principles of Planetary Climate" by Ray Pierrehumbert.
  22. Something that just came out, and may have an impact:

    http://www.sciencedaily.com/releases/2011/04/110421190450.htm

    Large dry ice deposits in Mars's South pole, that look as if they are currently in a dispersal phase - sublimating into the atmosphere as CO2.
    Response: [Dikran Marsupial] Activated link
  23. Do I understand correctly that Fenton 2007 was not based on actual measurements of temperatures on Mars, but rather an inference that temperatures must be going up because the albedo was lower? In my crude understanding (I have a bachelor's degree in mechanical engineering, but I work as an attorney and am by no means up on scientific trends in general, much less trends in climate science), the inference is that a lower *proportion* of light energy from the sun was being reflected, meaning a greater *proportion* of light energy from the sun was being absorbed, and therefore temperatures must be rising as a result? If I am getting this right, then to rely on Fenton 2007 as evidence that Mars warmed between 1977 and 1999, wouldn't you have to accept in the first instance that albedo is a reliable measure of Mars temperature, and doesn't that theory imply that the TSI is fairly constant (for the moment passing over StanislavLem's comment about other solar phenomena besides TSI impacting Martian climate)? Otherwise couldn't the perceived decrease in brightness on Mars actually be due to a decrease in TSI rather than a lower proportion of TSI that is reflected? If that were the case, that would undermine the argument that the Earth is heating up *because* of solar changes, as the Earth would be heating up *despite* a decrease in TSI. Of course, if we are actually measuring TSI directly, then the foregoing line of reasoning is irrelevant, and please forgive my ignorance.

    Turning to StanislavLem's comment about other solar phenomena causing dust storms on Mars, reasoning that those are "possible" on Earth as well, is anybody putting forth a cogent theory that dust storms on Earth actually are happening, that they follow the patterns of dust storms on Mars, and that they impact Earth's climate in a significant way?

    Is there a general consensus that the only actual significant heat energy from the sun is from TSI, even if other solar phenomena might have other impacts (gravitational/magnetic?) that could indirectly affect climate?
    Response: TSI is indeed measured by directly, by spacecraft.
  24. What I am trying to drive at with my last question is that if in fact TSI is relatively constant over the past several decades (which I assume scientists agree that it is, otherwise how could you make inferences about temperature change between 1977 and 1999 based on changes in brightness of a planet?) and is the accepted measure of heat energy emanating from the sun, it would seem that the burden of proof is on the proponents of Mars as a model for Earth to show more than just a laundry list of similarities between Earth and Mars, but rather a complete theory on how "other" solar effects are altering both Earth and Mars in the same ways.

    In saying that, I am not ruling out that an empirical close correlation in climate trends between Mars and Earth could persuade me that there is something to the solar effects theories, but my impression from the comment thread is that there has been no clear showing that the trends on Mars and Earth have been parallel.
    Response: You are correct. There are no clear parallels of trends in global temperature between Earth and other planets. In some limited time periods (pretty much random snapshots) we have some idea of some few other planets' temperatures. Comparing across those too-few snapshots reveals some of those few planets might be warmer and others might be colder. So skeptics who claim "other planets are warming just like Earth" are plain wrong.
  25. Moderator, thanks for the nearly instantaneous response to my post #23!
    Response: You're welcome, but I forgot to point you to the Skeptical Science post "It’s the sun" for more info about TSI.
  26. Just wanted to add to this thread the study that posits Uranus cooling from 1983 to 1998.

    "The secular increase in temperature seen during the
    period 1977–1983 has reversed."

    http://www.boulder.swri.edu/~layoung/eprint/ur149/Young2001Uranus.pdf

    I brought this up at WUWT a few years ago when this meme was being trotted out more often, and the responses were that Uranus has particular orbital characteristics that might account for its 'anomalous' climate behaviour.

    When I replied that other planets may likewise have characteristics particular to them that account for (apparent) warming, no one responded.
  27. While extraterrestrial climates and weather are interesting in their own right, and atmospheric compositions and temperature responses can be used to calibrate physical models here on Earth, it is irrelevant to us here whether or not it is warming on them as a result of the sun's varying output - we have infinitely better measurements of solar radiation here and its effect on our planet, which is what matters.

    It's just an invention that denialists use to try to mislead gullible people with something that sounds believable without all the facts.

    Whatever other planets are doing, in spite of the Sun's output having been at its lowest for years, our Earth is still warming.
  28. Interesting thread people.

    But one slight problem - I have been watching Mars since a young lad in the Apollo moon landings.

    Look at the photos of Mars in the 1970's - big beautifol really obvious ice caps. Now look at Mars - pathetic small and mostly non-existent ice caps. Why?

    [snip]
    Response: [Dikran Marsupial] Off-topic gish gallop snipped. Please familiarise yourself with the comments policy. SkS is for scientific discussion, not rhetorical debate. Data and references to scientific litterature that support your assertions are always much more convincing than anecdotal evidence.
  29. Well, let's look at the photos, or images at least:

    Mars, 1873:



    Mars, 2007:



    So from 1873 to 2007, Mar's NH polar cap has approximately the same size, while its SH polar cap has greatly expanded.

    But what about images like this:



    According to AGW denier, Nasif Nahle, this is a ...

    "Sequence of photos illustrating the Global Warming on Mars. Observe how Mars' Polar Caps have been melting since 1990, the same phenomenon has been occurring on Earth."


    Except, when I look at the pictures, I see the large expansion of the SH polar cap from 1995-2001, followed by its contraction. I also see the initial contraction of the NH polar cap, followed by its expansion, after which it is hard to say what it does because it is hidden behind the limb of the planet.

    Clearly, the polar caps of Mars are very dynamic. The rapidity with which they change their extent can be seen in this montage showing the NH cap over a period of six months:



    As we know, by 2001,it had already regained its lost extent, and no doubt lost it again before regaining it in 2007.

    AGW deniers, like Nahle, are attempting to portray images of seasonal variation as proof of global warming on Mars. But if you look at all the evidence, its easy to see through their parlour trick.
  30. Scott Duncan #28: "pathetic small and mostly non-existent ice caps."

    This is really big news, or at least it was in 2003: Mars is melting

    Like Earth, Mars has seasons that cause its polar caps to wax and wane. "It's late spring at the south pole of Mars," says planetary scientist Dave Smith of the Goddard Space Flight Center. "The polar cap is receding because the springtime sun is shining on it."

    The south pole is indeed more dynamic:

    The coincidence of aphelion with northern summer solstice means that the climate in the northern hemisphere is more temperate than in the southern hemisphere. In the south, summers are hot and quick, winters long and cold.

    Seasons! Who'd have thought that?
  31. I'm a bit bored, so I've decided to actually show the "big beautifol really obvious ice caps" Duncan claims to have seen in the 70's.

    First from the Mariner missions in 1969:



    The two images where taken be separate craft on flybys, within six days of each other in 1969.

    Then from the Viking program in 1980:



    Viking even produced a mosaic map of Mars, showing the massive polar ice caps that existed just 30 years ago:



    If you think I am laughing at the intellectual bankruptcy of deniers like Nahle who try to flog this dead horse, you are right.
  32. Thank you Tom, this is the point I was trying to convey in post #11 up there a few years ago. Intellectual bankruptcy is the word indeed.
  33.         Thinking 'outside the box' is a school not often visited by some.   In all the discussions of planetary global warming (i.e.  Earth, Mars Jupiter, Saturn, Pluto) very little attention is given to our solar system's travel above, below, and around the galactic plane on its cyclical route round the Galaxy. (approx 240k+ years).  Conditions along the path are hard to predict since historic records are only now being established.  Therefore any theories or calculations of planetary temperatures from volcanic, atmospheres, rings of dust, or human intereactions, etc. must include calculations of the density and  position of materials encountered along our solar systems path and its interactions with the Sun's activities.  These conditions make it extremely difficult to predict any astronomical algorithm's absolute forecasting the reason for Earth's warming trends.  In other words,  the best thought humans put forth probably has not reached a definite answer in totallity to the question, "Why is Earth warming?" 

  34. Whether travels on the galactic path had anything to do with past climate change is harder to decide, but we can see clearly that it has very little to do with post-1970 climate change. Why? because we have good measurements of the climate determinants. The only "space" factor affecting climate is TSI, whether from change of angle, change of solar luminense or "space dust". This is accurately measured by satellites since 70's and is stable if not decreasing (see "its the sun" argument), and yet the earth warms. Why look to weird, unknowable, out-there sources of warming when there is a perfectly reasonable, physically plausible solution coming right out of the smoke stack? Or to put it another way, we have measurably increased the energy flux onto the surface of the earth with increased GHGs. What mechanism do you propose by which this would not cause warming?

  35. We have NOT been measuring the other planets temperatures systematically since the 70's.... and I did not state the the majority of EARTH warming does originate with our mismanagement of the planet.  I was only stating that IF other planets in our system might all be experiencing warming, then we should  look at other possibilities be they "weird" or undiscovered! 

  36. Novemdecellist @33, there is a very simple reason to think that our motion through the galaxy has very little do do with current changes in climate.  Specifically, it will take us 1360 years to travel just one light year at our current rate of travell.  In the direction we are travelling, there are no nebulae to obscuring local stars, so we know the nearest nebula to be many light years away.  Apparently the nearest nebula of any sort, L134, is around 300 light years away, and not in our direction of travel.

    It follows from this that the radiation, and molecular density of the space through which we are travelling has not changed appreciably in hundreds of thousands of year; and will not change appreciably for hundreds for thousands more years except in the cases of nearby supernovas.  And if it is not changing, it is not the cause of change.

  37. And also worth noting (as this and articles on other planets show) that real evidence for climate change on the other planets is somewhat lacking. See the intermediate versions.

  38. Also worth noting are the astronomers - who spend their careers looking at the stars, including spectral and intensity measurements. If we had entered a nebula (that was somehow unobserved at a distance) the reduction in starlight over the last 40 years would have been quite noticeable. Not to mention spectral changes in sunlight, measured either from the surface or from satellite. 

    Given a complete lack of evidence for a hypothesis of interstellar dust/climate interaction, I would classify it on the same level as "climate elves". 

  39. Novemdecillist...   Is there something to give you indication that others are not thinking outside this particular box?  I would suggest that scientists have made careers out of looking into a wide range of boxes to see if there could possibly be other explanations for what they see.  In fact, other planets warming would be one of the first in a long series of other boxes researchers would check into.

  40. Tom Curtis #29:

    If all the photos in your figure 3 were taken close to opposition (when Mars is closest to the Earth), each of them must have been taken about 780 days later than the previous one, or one Martian year plus 93 days. That is like taking photos of the Earth with 415 days intervals or 50 days later every year.

    Based on the surface markings it seems to me that the photo from 2001 must have been taken close to northern hemisphere autumn equinox on Mars, corresponding to late September on Earth.

    That means that the photos from 1995, 1997 and 1999 roughly corresponds to late April, mid June and early August respectively (spring and summer in NH), while the photos from 2003 and 2005 corresponds to early November and late December (spring and summer in SH).

    In other words, the changes in this photo sequence are simply caused by the seasons, and have nothing to do with any climate change on Mars!

    I wonder how this guy Nasif Nahle would explain away that?

  41. HK @40, you raise a very good point.  It is likely that most of the differences between polar cap size in Mar's observations will be due to seasonal cycles, something Nahle has failed to consider (along with the majority of the evidence on the changes in the size of Mars's icecaps over time.

  42. Thank you for a quick response, Tom!

    Yes, it is meaningless to use photo sequences like that as proof of climate change on Mars unless the photos are taken close to one Martian year (687 days) apart. In the 2005 photo, the south polar cap (mostly frozen CO2) had been exposed to the midnight sun for nearly 6 months. No wonder it had almost disappeared!

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