At a glance – Is Mars warming?

Posted on 7 November 2023 by John Mason, BaerbelW

On February 14, 2023 we announced our Rebuttal Update Project. This included an ask for feedback about the added “At a glance” section in the updated basic rebuttal versions. This weekly blog post series highlights this new section of one of the updated basic rebuttal versions and serves as a “bump” for our ask. This week features “Is Mars warming?“. More will follow in the upcoming weeks. Please follow the Further Reading link at the bottom to read the full rebuttal and to join the discussion in the comment thread there.

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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