2010-09-05 21:11:17Basic rebuttal 48: Neptune is warming
Graham Wayne

Argument 48: Neptune is warming

The argument is this; other planets are warming. If this is happening throughout the solar system, clearly it must be the sun causing the rise in temperatures – including here on Earth.

It is curious that the theory depends so much on sparse information – what we know about the climates on other planets and their history – yet its proponents resolutely ignore the most compelling evidence against the notion. Over the last fifty years, the sun’s output has decreased slightly: it is radiating less heat. We can measure the various activities of the sun pretty accurately from here on Earth, or from orbit above it, so it is hard to ignore the discrepancy between the facts and the sceptical argument that the sun is causing the rise in temperatures.

TSI from 1880 to 1978 from Solanki. TSI from 1979 to 2009 from PMOD.

But if the sun’s output has levelled off or even diminished, then what is causing other planets to warm up? Are they warming at all?

The planets and moons that are claimed to be warming total roughly eight out of dozens of large bodies in the solar system. Some, like Uranus, may be cooling. All the outer planets have vastly longer orbital periods than Earth, so any climate change on them may be seasonal. Saturn and its moons take 30 Earth years to orbit the Sun, so three decades of observations equates to only 1 Saturnian year. Uranus has an 84-year orbit and 98° axial tilt, so its seasons are extreme. Neptune has not yet completed a single orbit since its discovery in 1846.

This is a round-up of the planets said by sceptics to be experiencing climate change:

  • Mars: the notion that Mars is warming came from an unfortunate conflation of weather and climate. Based on two pictures taken 22 years apart, assumptions were made that have not proved to be reliable. There is currently no evidence to support claims that Mars is warming at all. (Specific aspects of the 'Mars' argument are addressed in a separate post "Global Warming on Mars?")
  • Jupiter: the notion that Jupiter is warming is actually based on predictions, since no warming has actually been observed. Climate models predict temperature increases along the equator and cooling at the poles. It is believed these changes will be catalysed by storms that merge into one super-storm, inhibiting the planet’s ability to mix heat. Sceptical arguments have ignored the fact this is not a phenomenon we have observed, and that the modelled forcing is storm and dust movements, not changes in solar radiation.
  • Neptune: observations of changes in luminosity on the surface of both Neptune and its largest moon, Triton, have been taken to indicate warming caused by increased solar activity. In fact, the brightening is due to the planet’s seasons changing, but very slowly. Summer is coming to Neptune’s southern hemisphere, bringing more sunlight, as it does every 164 years.
  • Pluto: the warming exhibited by Pluto is not really understood. Pluto’s seasons are the least understood of all: its existence has only been known for a third of its 248 -year orbit, and it has never been visited by a space probe. The ‘evidence’ for climate change consists of just two observations made in 1988 and 2002. That’s equivalent to observing the Earth’s weather for just three weeks out of the year. Various theories suggest its highly elliptical orbit may play a part, as could the large angle of its rotational axis. One recent paper suggests the length of Pluto’s orbit is a key factor, as with Neptune. Sunlight at Pluto is 900 times weaker than it is at the Earth.

Claims that solar system bodies are heating up due to increased solar activity are clearly wrong. The sun’s output has declined in recent decades. Only Pluto and Neptune are exhibiting increased brightness. Heating attributed to other solar bodies remains unproven.

2010-09-05 21:21:03Notes
Graham Wayne

Because there is so very little to say about individual planets, I've written one text and used it for the Jupiter, Neptune and Pluto basic rebuttals, changing the bullet point order so the specific planet is the first in the list depending on which argument you look up. This text in turn is taken from a slightly expanded version done for the 'solar system' argument. Hope this is acceptible...

(PS - Mars has a full rebuttal of its own)

2010-09-05 23:28:44Some typos


Hi Graham,

having basically the same text for each planet makes sense to me - and it will make life easier for the translators as well!

I spotted some typos:

2nd paragraph - moons should be plural
"....- roughly 6 planets or moons out of 100 bodies"

"...by sceptics " --> do we have a decision yet of how to spell "sceptic" on "SkepticalScience"?

Bullet-point about Jupiter:
"Sceptical arguments have ignored the fact that this is not a phenomenon we have observed,... " --> it may just be me, but I think the sentence reads better with "that" included

Bullet-point about Pluto:
"...so it may be seasonal. Sunlight at Pluto is 900 times weaker than it is at the Earth."


2010-09-06 00:25:43Another point


is that the more remote planets have very long planetary years: Many many decades.

So even if some of them are warming, this cannot be distinguished from a seasonal effect without a few planetary cycles.

2010-09-06 00:39:53Corrections
Graham Wayne
Indeed Baerbel - thanks again for sharp proofreading. All issues now addressed - and it will be 'skeptics' when the style guide comes out, to match the site title. I intended to use that spelling but MS Word changed it behind my back!
2010-09-06 06:22:43


Might change "...be causing warming anywhere, including on Earth. " --> "...be causing increased warming anywhere, including on Earth. " just to arrest cheap shots. Granted that "warming" implicitly states the obvious but that won't stop quibblers. 

Optional, gets my vote! 


2010-09-06 16:41:44I agree
Graham Wayne

I agree Doug - I'm always keen to head them off at the pass, as it were. The slightest gap and some silly bugger will try to squeeze through it with a surly grin and an insult...

Neal - that is already mentioned twice, in the Neptune and Pluto items. I think that covers it sufficiently, as it isn't the explanation or rebuttal for two out of the four illustrations. Further emphasis might be misleading.

2010-09-07 17:03:01Mention cooler sun.


Good idea on joining all the individual planets into one rebuttal. 

You could mention that the sun has actually cooled off. Further, the sun goes through regular cycles of cooling and warming which do not match the warming up of any planet.


2010-09-07 23:56:15


 I sugget the following changes, those mentioned above, plus:

"heating attributed to other solar bodies are unproven."   to  "heating attributed to other solar bodies is unproven.' (subject is the singular "heating" in penultimate paragraph.


Very good, clear, complete. Using same basic text for all planets, or grouping all planets into one rebuttal are both reasonable solutions. 

You win a thumb from me. 

2010-09-09 04:20:35Approve

Ok, let's go
2010-09-09 12:06:39Go ahead.


A mere quibble. You may want to place the planets in order of distance from the sun. Mars, Jupiter, Neptune and Pluto. Otherwise it's perfect.


2010-09-10 01:36:42I agree with Neal
James Wight

We really should emphasize how short a time we’ve been observing the outer planets compared to even one seasonal cycle. It shows just how ridiculous it is for contrarians to claim we know the climates of those planets are changing. See my post on the "Other planets are warming" thread.
2010-09-10 14:02:55Comment
Robert Way

good to go!
2010-09-11 00:16:08Revisions done
Graham Wayne
OK - I've updated all these rebuttals, but they are all identical now. Could you please comment only on the post Basic rebuttal 25: Other planets in the solar system are warming - just to keept things all in one place .