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Do we have a few decades worth of surface temperature data to compare?

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  • $\begingroup$ It is hard enough getting measurements of global mean temperatures on Earth. $\endgroup$ – Rob Jeffries Feb 8 '16 at 19:03
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The short answer to your question is "decades", only for Mars, and only a two Mars decades (about 4 Earth decades)

I don't know if your question was related to climate change, as there were a number of extremely unscientific arguments made that Pluto and Mars are getting warmer, "and there are no SUV's on Mars" . . . so, maybe it's not the CO2 but those claims weren't science.

Silly articles and bad arguments aside, global temperature on other planets is a legit scientific question and there were scientific articles that said Pluto is getting warmer (2002, story below) and Mars is getting warmer (2007, also below), so there is some truth to this. I'll give an answer as best I can. Each planet deserves it's own bit of research, so this will be longish.

Pluto

Here's an article on Pluto, the title is iffy but the article is good. It's from 2002, so it's long before New Horizon's fly-by, it's even before New Horizon was launched, but "pluto is getting warmer" was a real scientific story in 2002, and Mars, in 2007 was real science too, but some of the conclusions drawn, loosely based on those two stories were ridiculously bad.

The gist of the article is, we can't see Pluto's atmosphere well, even with Hubble, but they were able to measure some aspects of Pluto's atmosphere by watching what happens when a star passes behind Pluto and that was measured twice, in 1988 and again in 1997.

Pluto's Perihelion was in 1989 and most everyone figured that the little ball of ice/dwarf planet would get colder after 1989 when it passed it's closest point to the sun and stated moving further away but the readings said otherwise, and that was one of those really cool "oh, wow, things are more interesting than we thought they were" moments. Pluto's atmosphere had apparently gotten thicker and it was about 2 degrees warmer. Not what anyone expected.

The problem is, the sun couldn't make Pluto 2 degrees warmer while it moved further away without making the Earth 20 degrees warmer at the same time, so, clearly, something else was at play and it wasn't the sun warming Pluto. Generally speaking, the warmest periods aren't necessarily precisely timed to closest to the sun, and there's a lag time caused (on Pluto) by sublimation of the frozen gases on it's surface, which thickens the atmosphere adds trace amounts of Methane and can warms the planet past Pluto's perihelion, just as on the Earth, June 21 isn't the warmest day on the Northern Hemisphere, nor December 21st the coldest, and 12:00 noon isn't the hottest time. Could that seasonal "lag time", apply over a number of Earth years on Pluto? It's plausible.

But we should remember, that's just two data points, which isn't nearly enough. Or, 3 data points now with New Horizons, but it's still just 3 data points spanning 27 years on a planet where one year is 248 earth-years, so, there's a lot we don't know about seasons on Pluto.

New Horizons got better data on Pluto's atmosphere and frozen surface than we've ever had before, and what I remember reading about it, though I'm very far from well read on the subject, is that Pluto has a much more dynamic atmosphere and surface than anyone expected.

Gas Giants

you asked:

Do we have a few decades worth of surface temperature data to compare?

Surface temperature isn't well defined on gas giant planets because we can't see the surface. Also (I think all 4, I know for sure Jupiter and Neptune), they give off more heat internally than they receive from the sun. Temperature on the visible surfaces / upper atmospheres of the gas giants has more to do with circulation than anything else.

Mars

There's a number of articles on Mars warming, but there's still a lot we don't know about Mars' climate. It's not too difficult using modern technology and with Mars' thin atmosphere, to read surface temperature on Mars by measuring the infra red light that comes from it's surface. The surface temperature on Mars was first measured in 1920 (see 4th paragraph from the top), and NASA says here that they've been taking accurate surface temperature readings on Mars for 30 years (article from May 2007), so it's pretty safe to say we have about 38-39 Earth years (20 or so Mars years) of reasonably good global temperature readings on Mars and a few decades more than that with less accuracy.

There's many problems with reaching any kind of conclusion on Mars based on that data though. Mars has significantly greater eccentricity than Earth, so it may be prone to larger temperature swings than Earth and just 20 Mars years of data is too few.

Winter to Summer on Mars' enough CO2 can freeze to reduce it's atmosphere by as much as 25% and that can drive temperature changes and mars is also prone to planet wide dust storms that can last months. These can have the effect of blocking sunlight and after settling, darkening the ice caps, which lowers albedo. Like Pluto, Mars' atmosphere, climate, temperature and orbit are dynamic and there's still a lot we don't know about how they worth together to form a predictable climate on Mars.

As an FYI, dust storms are nothing like in the movie the Martian, but they can cause a visible haze over the planet that can obscure viewing it's surface. A nice short article on Mars' dust storms here and here.

I think it's kind of cool that Mars forms an annual "cloud", not unlike how parts of Earth form annual snow and ice covers in winter that thaw in Summer, but we don't know nearly enough about Mars, even with 20 Mars years of observation, to make good long term predictions on Mars' climate.

Venus

Venus, as far as I know, pretty much never changes. It's the same temperature, Winter, Summer, Pole, Equator. There might be some slight variation of Venus temperature depending on elevation, like the gas giants, but I'm not sure. Venus traps heat so effectively that is changes very little, in fact, I've never seen one article mentioning Venus' surface temperature changing as much as 1 degree. Venus reflects most of the sunlight that hits it away anyway, so it would be less prone to solar variation anyway.

I won't do Mercury cause I don't know enough about it, but that's 7 out of 8 anyway.

. . .

If your question is about having a good understanding of climates on other planets, then decades of surface temperature data wouldn't be enough even if we did have it. Centuries of accurate surface temperature data, you could begin to recognize patterns, for the inner 4 planets anyway, but decades isn't enough to differentiate between a baseline, a natural fluctuation or a transition period.

If anyone tells you there are no SUV's on mars, so how could Mars be warming, get away from them as fast as you can. They're not interested in science.

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  • $\begingroup$ Thanks for your thorought answer. I have no agenda other than to get the cold facts of science on the matter. $\endgroup$ – Logray Feb 12 '16 at 15:20
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Pluto is currently cooling down, since its distance from the Sun is increasing now, a few years after perihelion. That's seasonal.

Mars has been suspected to warm up. But as far as I know, that's questioned in the meanwhile.

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