2010-08-17 19:42:02Basic rebuttal No. 19: Mars is warming - REVISED
Graham Wayne
Dust-Up On Mars: Should Martians Be Sceptical of Global Warming?
Argument No. 19: Mars is warming

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 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 is 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.

2010-08-17 20:37:17
Anne-Marie Blackburn
Anne-Marie Blackburn
I think it's excellent and very clear - ready to go I'd say, though I know some contributors would prefer shorter rebuttals.
2010-08-18 02:13:58Great treatment


Comprehensive, and it -has- to be. Some of these rebuttals need to delve into details if they're not to sound like "is so!" ... "is not!" kid talk.

"Mars is warming" is a rather esoteric skeptic argument so it's not surprising even a basic rebuttal will require more depth.

2010-08-18 02:53:22done
Robert Way

Good post
2010-08-18 06:58:44
Andy S

Yes, that's really good. I started reading it knowing nothing about the subject and came away having learned a lot.
2010-08-18 09:07:33
Michael Searcy


I like it.  It provides a lot of great information.  However, I'm wondering if it gets into a bit too much detail for the basic argument.  Here's a version I wrote up a while back on the subject.

If Mars is experiencing warming on a global scale, the only reason to discuss it alongside planetary warming on Earth is to attribute both warming trends to a common source, namely the Sun. However, the output of the Sun has not increased noticeably over the last 30 years of direct observation.

The discussion of solar climate forcing also detracts from the much more obvious fact that Mars is a completely different planet from Earth. Mars is a unique planet with vastly different compositions to its atmosphere, wind currents, orbital variations, rotational characteristics, weather patterns, and so on. In other words, at any given time, the Martian climate is exposed to forcings that are literally a world away from those impacting Earth. The two planets could be warming concurrently, cooling concurrently, or going in completely opposite directions based on purely natural influences. As a result, there is little validity in drawing a parallel between the two planets to deduce a cause of warming here on Earth.

Due to the vastly different composition of the Martian atmosphere, it is prone to massive dust storms that can greatly affect planetary temperatures. These dust storms also impact the albedo of the Martian surface, enabling the planet to retain more heat without a concurrent rise in solar output. And it is these atmospheric characteristics of Mars that are being found responsible for the recently observed melting of the polar ice caps on that planet.

2010-08-18 09:31:58


I found it very good too! Very clear.

One minor thing I found a little awkward was ...

There are more times when Mars is closer to the sun, and more times when it is further away.

"More times" is a bit obscure, when I first read it, given the previous sentence comparing variations ibetween Mars and Earth, I thought you were saying Mars could be closer to the sun than Earth (obviously you're not suggesting that, but that's how it struck me and perhaps others might mis-interpret this?).

I would reword that paragraph as :

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.

But otherwise I think it's great.

2010-08-18 15:19:24Eccentric writing
Graham Wayne
Brendon - I agree. Changed the text accordingly (I know what I meant, but it didn't quite come out that way!) :)
2010-08-20 12:39:26Viking, not Voyager
James Wight

Graham, the Voyager probes never went anywhere near Mars. The only spacecraft orbiting Mars in 1977 were the Viking probes, so it must have been one of both of them that took the photos.
2010-08-20 16:28:05Which spacecraft
Graham Wayne

Hi James - I took that straight from the intermediate version but I've now checked the Gessler paper and you are quite right - I've already changed the text accordingly, but the intermediate version will also need correction (I've notified JC).

2010-08-21 02:30:35Excellent
John Russell



It's excellent. Just one teeny, weeny comment that might help on some of your other writings too. You have a tendency to leave out the word 'that' in places where its inclusion would help. Example (from para two)...

 "we know so little about Mars (that) it is impossible to say what trends in climate the planet is experiencing"

I'm really starting to worry about my reputation.  I can't help it that these things stand out like chapel hatpegs to me and make my teeth grate. What a sad old git. 

Best wishes,


PS: I've awarded it the green thumb.

2010-08-21 11:36:31Published
John Cook

I also did John Russell's grammatical correction. Don't worry, JR, I'm obsessive about those kinds of things too. Having a background in graphic design, I'm always pointing out when people don't use proper typographical inverted commas on TV and on flyers. Must make me real difficult to live with :-)
2010-08-22 01:08:07Aaahhhh
Graham Wayne
...anything to make an old man happy... :)