Arguments
Is Mars warming?
What the science says...
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Mars is not warming globally. |
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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.
At a glance
You really have to hand it to climate science deniers. In the one breath, they claim global warming on Earth is all down to poor/badly-sited weather-station coverage. Then in the next, they assert that Mars is warming. How many weather stations are there on Mars? In that sense, this claim serves to point out the absurd depths that climate science deniers plumb at times.
But in another sense, it offers the opportunity to explore why the climates of Earth and its neighbour differ so much. For, in times long past, Mars had an atmosphere and running water in abundance. Not any more. It is a cold, dry and - so far as we know - dead planet.
We know there was water there on Mars from the layered, river- or lake-deposited sedimentary rocks there, examined by robotic landers. What happened to it? The answer lies in the Red Planet's global magnetic field. It collapsed billions of years ago.
Why Earth still retains a strong global magnetic field but Mars does not is still the subject of much research. What we do know is that on our planet the spinning, liquid metal outer core acts as a powerful dynamo. Our thus-generated global magnetic field works as a vital planetary shield against the Solar wind and cosmic rays. In contrast, Mars has little such protection any more: long ago, once it lost that shield, the vast majority of its atmosphere was stripped away by those Solar winds.
No atmosphere, no greenhouse effect as such. Mars instead experiences extremes of heat and cold (from -153 to +20 C according to NASA) depending on what part of the planet is facing the Sun - and constant drought. Long lived, sometimes planet-wide dust-storms can occur when the dry ground becomes especially warm, even on a planet whose atmosphere has a density of just 1% of Earth's. Because of that very low density, atmospheric pressure on the Martian surface is a fraction of that on Earth and winds are much lighter, but combine a stiff breeze, plentiful dust and the fact that hot air rises (hence dust devils, observed by those robotic landers) and you have the mechanism for getting that dust up.
In turn, the dust blocks some sunlight from getting down to the surface, so here we have a temperature regulating mechanism. But even the biggest dust-storms - that can be viewed with telescopes here on Earth - end at some point. Mars therefore has no long-term temperature trend but its inhospitable climate nevertheless varies - but for completely different reasons than here on Earth.
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Further details
The motive for making inaccurate claims about other planets also experiencing warming is not hard to imagine: it's yet another variant of the "it's the Sun" family of arguments. All members of this group of myths depend on Solar irradiance steadily going up and up through time. Yes that does happen, hence the Faint Young Sun paradox, but there we're talking about a trend only detectable over geological timescales, not centuries.
As fig. 1 shows, in fact from around the mid 1970s onwards, global temperatures have risen while total Solar irradiance has declined. So that puts the "it's the Sun" family of arguments straight to bed.
Figure 1: Annual global temperature change (thin light red) with 11 year moving average of temperature (thick dark red). Temperature from NASA GISS. Annual Total Solar Irradiance (thin light blue) with 11 year moving average of TSI (thick dark blue). TSI from 1880 to 1978 from Krivova et al. 2007. TSI from 1979 to 2015 from the World Radiation Center (see their PMOD index page for data updates). Plots of the most recent solar irradiance can be found at the Laboratory for Atmospheric and Space Physics LISIRD site.
With specific regard to Mars, it can readily be counter-argued that we know so little about Mars - compared to Earth - that we cannot yet talk about things like temperature trends. We just don't have the details, even though the orbiters and robotic landers are providing valuable and fascinating insights into some aspects of the Red Planet. Yet even this so far small amount of data can be misinterpreted, in terms of causal complexity and significance. And that's a funny thing about climate science denial. Its practitioners cast all sorts of aspersions regarding temperature measurements here on Earth, but in the case of Mars, all of a sudden their expectations are somewhat lowered, so this time they base their claims on limited spatial coverage and direct measurements taken over only a few decades.
There are, however, a few general points about the climate on Mars that are worth listing:
- 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.That's because the Martian orbit varies in eccentricity by over five times more 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. Because of that very thin atmosphere, the planetary greenhouse effect is also of negligible importance.
- The whole planet is subject to massive dust storms, and these have many causal effects on the planet’s climate, aspects of which we don't understand yet. However we do know that on Earth dust-clouds can reduce the sunlight (and therefore heat energy) reaching the surface.
- 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.
The 'global warming on Mars' argument had at least some of its roots in a paper written by a NASA team, entitled, "Global warming and climate forcing by recent albedo changes on Mars" (Fenton et al. 2007). But this paper is about changes in Martian albedo - the property of light surfaces to reflect incoming sunlight, Variations in brightness of parts of the Martian surface have been recorded ever since we have had telescopes powerful enough to look at the planet in detail.
The study compared pictures of the Martian surface taken in 1977 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 et al used a general circulation model to investigate further.
Results indicated the presence of relatively enhanced wind stress in recently darkened areas and decreased wind stress in brightened areas. This produced a positive feedback system in which the albedo changes strengthen the winds that generate the changes. The simulations also predicted a net annual global warming of surface air temperatures by ∼0.65 K over that 22-year period (the abstract was a bit confusing on this point - see corrigendum here), enhancing dust lifting by increasing the likelihood of dust devil generation. The increase in global dust lifting by both wind stress and dust devils may, they thought, affect the mechanisms that trigger large dust storm initiation, a poorly understood phenomenon, unique to Mars. They suggested that documented albedo changes affect recent climate change and large-scale weather patterns on Mars, and thus albedo variations are a necessary component of future Martian atmospheric and climate studies.
Let me repeat part of the last but one sentence above: "unique to Mars". That's right there, in the abstract. Neither the Martian atmosphere, environment nor climate are remotely like anything on Earth. Yes, albedo-change is important on Earth but is a feedback driven by other forcings unrelated to Martian goings-on. Furthermore, a 22-year long study-period with two endpoints and nothing much in between is not robust in terms of a climatic trend.
Indeed in a recently published paper (Scariah et al. 2023), analysis of the seasonal variation of evening temperature over Gale Crater and its surroundings from Martian years MY 12 to MY 35 (equivalent Earth years 1976–2020) was carried out using data from different orbiter missions. The data showed variability (including significant drops in temperature during MY 26 and MY 32) but a trend? No.
To conclude: Mars' cold, arid climate is primarily driven in the long term by orbital eccentricity and in the short term by changes involving dust and albedo, not solar variations. In any case, we know the sun is not heating up the planets in our solar system because we can accurately measure the sun’s output, both here on Earth and in nearby space.
Last updated on 29 October 2023 by John Mason. View Archives
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?"
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?
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!
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.
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.
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".
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.
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?
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.
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!
Hi There, I know it has been a couple of years, but since bad arguments against AGW tend to stick around, I recently tried to explain to someone how mars' specific characteristics make it a bad earth analog in this case. I was then tripped up by the fact that we do use Venus as an analog for the greenhouse effect. I'm sure there's an explanation of how these things do not refute each other, how it isn't hypocritical to use both concepts in explaining our understanding of AGW, but I'm having trouble wording it. Can anyone help me out. Why do we accept Venus as an example in support of AGW hypothesis, but reject Mars as an example in opposition. Thanks!
I think you need to explain your problem a little more. GHG play a part on both Venus and Mars. Exactly the same equations are used to calculate the change of surface temperature due to GHE on Venus, Mars, Earth (or any other planet). Try here for detailed comparisons. I dont see a claim that is using Venus to support AGW and Mars to reject it.
@43,
I would request a link to where Venus is used as an example of the greenhouse effect, thanx !!
Well Venus is hardly an "analog". It is often used as an example of a "runaway greenhouse effect" - positive feedback boiling oceans and then remaining too hot for condensing of any GH gases. Note that scientific opinion so far is that there is no chance of this happening here due to anthropomorphic activities.
A good discussion of Venus' greenhouse effect is here, by Chris Colose.
GPWayne, your link to Fred Thompson in the green box no longer works.
[GT] Thanks, we will update the link.
Dutchwayne @49 - you are certainly correct that Mars is a far simpler climate system. But given the very great differences between it and Earth, it is therefore a much poorer comparison to Earth's system. So therefore what useful information can be gained in the comparison, which could not be better obtained elsewhere?
For instance: solar activity is better measured directly by Earth satellite, rather than by observation of its effects on a planet which is (varyingly) 60 million to 400 million Km from Earth.