Mars melt and Global Warming

[FireGarden]

http://news.nationalgeographic.com/news/2007/02/070228-mars-warming.html

Mars Melt Hints at Solar, Not Human, Cause for Warming, Scientist Says

Simultaneous warming on Earth and Mars suggests that our planet's recent climate changes have a natural—and not a human-induced—cause, according to one scientist's controversial theory.

[...] Abdussamatov's work, however, has not been well received by other climate scientists.

[...] The conventional theory is that climate changes on Mars can be explained primarily by small alterations in the planet's orbit and tilt, not by changes in the sun.

"Wobbles in the orbit of Mars are the main cause of its climate change in the current era," Oxford's Wilson explained.

 

[Buckaroo]

http://news.nationalgeographic.com/news/2007/02/070228-mars-warming.html

Mars Melt Hints at Solar, Not Human, Cause for Warming, Scientist Says

Absolute nonsense. The Martian ice caps are well-known for their variability. They're frequently barely even there.

 

[Fnord]

No wobbles in Earth's orbit? No precession in its rotational axis? No drift or variations in the Earth's magnetic field? No variations in the solar flux?

Yep. Gotta be them thar deesil injins wutt keeps rollin past my double-wide!

 

[Brian the Snail]

1. As mentioned in the article, the entire evidence for global warming on Mars are photos of the southern ice cap taken over three Martian years.

Now imagine that the only evidence of global warming on Earth was melting of an ice-cap over three years. No indication of whether it is part of a longer trend. No indication whether this warming was global or only local in scale. I know I would be very skeptical of global warming in this case. That's even before we attempt to assign causes.

To be a skeptic means being balanced in your skepticism. Not latch onto something on the flimsiest of pretexts, but ignore more overwhelming evidence elsewhere.

2. The sun's luminosity has been monitored by satellites over the past thirty years , and there's no overall trend (see Figures 1 and 4 in link). So how can someone blame the Sun for warming on Mars or Earth during that period?

 

[Fnord]

So how can someone blame the Sun for warming on Mars or Earth during that period?

For that matter, how can any one contributing cause be singled out as the sole cause for global warming, whether on Earth, Mars, or Planet X?

May as well place the blame solely on bovine flatulence...

 

[Brian the Snail]

For that matter, how can any one contributing cause be singled out as the sole cause for global warming, whether on Earth, Mars, or Planet X?

May as well place the blame solely on bovine flatulence...

Nobody is saying that there's a sole cause for global warming on Earth. Certainly not the climate scientists, anyway. They're saying that the dominant cause over the past few decades is greenhouse gas emissions from human activity.

 

[shanek]

No wobbles in Earth's orbit? No precession in its rotational axis? No drift or variations in the Earth's magnetic field? No variations in the solar flux?

I asked this question in another thread but got no answer: the current trend is warming in the northern hemisphere but cooling in the southern hemisphere and Antarctica. I once heard some astronomer-or-other (don't remember where, sorry) talk about procession and how traditionally we've been closer to the sun when it's summer in the southern hemisphere, and therefore the summers were warmer than normal; but now procession is taking us away from that and now summers in the southern hemisphere should be cooler and warmer in the northern hemisphere. How much of an effect would that have on the current climate readings?

 

[shanek]

Nobody is saying that there's a sole cause for global warming on Earth. Certainly not the climate scientists, anyway. They're saying that the dominant cause over the past few decades is greenhouse gas emissions from human activity.

But the planet's been warming for a lot more than a few decades. The current warm trend, in some figures, goes back to 1800. So what was the cause before us? What would the warming be now without our CO2 contributions, and how do we know that?

 

[Shabaz]

Nobody is saying that there's a sole cause for global warming on Earth. Certainly not the climate scientists, anyway. They're saying that the dominant cause over the past few decades is greenhouse gas emissions from human activity.

And to post the relevant chart from the last IPCC Fourth Assessment Report Summary to back Brian's statement up (I think this is the relevant chart, someone correct me if I'm wrong):

 

[Brian the Snail]

But the planet's been warming for a lot more than a few decades. The current warm trend, in some figures, goes back to 1800. So what was the cause before us?

Partly solar, partly changes in volcanic activity, partly GHG forcing.

See this figure for example.

What would the warming be now without our CO2 contributions, and how do we know that?

It would probably be cooling actually, due to the increasing sulphate aerosols, which reflect sunlight back into space. There has also been an increase in volcanic activity, which causes cooling for similar reasons.

 

[Shabaz]

I asked this question in another thread but got no answer: the current trend is warming in the northern hemisphere but cooling in the southern hemisphere and Antarctica. I once heard some astronomer-or-other (don't remember where, sorry) talk about procession and how traditionally we've been closer to the sun when it's summer in the southern hemisphere, and therefore the summers were warmer than normal; but now procession is taking us away from that and now summers in the southern hemisphere should be cooler and warmer in the northern hemisphere. How much of an effect would that have on the current climate readings?

Kind of out of my depth here, but I think those would be the Milankovitch Cycles. I'm pretty sure that they don't have a large enough effect to account for the observed warming trend that is commonly associated with global warming, but they're pretty relevant to the timing of glaciation periods. Can't post any links yet, but wikipedia should have a somewhat ok article on it.

 

[Brian the Snail]

I asked this question in another thread but got no answer: the current trend is warming in the northern hemisphere but cooling in the southern hemisphere and Antarctica. I once heard some astronomer-or-other (don't remember where, sorry) talk about procession and how traditionally we've been closer to the sun when it's summer in the southern hemisphere, and therefore the summers were warmer than normal; but now procession is taking us away from that and now summers in the southern hemisphere should be cooler and warmer in the northern hemisphere. How much of an effect would that have on the current climate readings?

It's not true that it's cooling in the southern hemisphere. It's warming, but at a slower rate than the NH. Some areas, such as parts of Antarctica have been cooling, however. See here.

In any case, the Earth's precession cycles have a period of about 20 000 years, which is far too slow to be causing the current climate changes. See this graph.

 

[shanek]

And to post the relevant chart from the last IPCC Fourth Assessment Report Summary to back Brian's statement up (I think this is the relevant chart, someone correct me if I'm wrong):

Where's water vapor? I thought it was a greenhouse gas, too?

 

[shanek]

Partly solar, partly changes in volcanic activity, partly GHG forcing.

See this figure for example.

Thanks! So nice to have a straight rational answer on this issue.

I have some more questions about this site then:

About this graphic: http://www.globalwarmingart.com/wiki/Image:IPCC_Radiative_Forcings_gif

It says that solar (which I would think is a very significant variable; I've been outside in an eclipse, after all) forcing is least understood. "Very low" scientific understanding, and all the way to the right of the graph. If that's the case, I would expect the error range for solar to be rather high. How much is actually known about solar effects?

Also, same question as above: where is water vapor? How much of an effect does it have, and why is it not included in the charts?

It would probably be cooling actually, due to the increasing sulphate aerosols, which reflect sunlight back into space. There has also been an increase in volcanic activity, which causes cooling for similar reasons.

I thought volcanoes put CO2 into the atmosphere? Or do they also put out enough sulfate aerosols to counteract it?

 

[shanek]

Kind of out of my depth here, but I think those would be the Milankovitch Cycles. I'm pretty sure that they don't have a large enough effect to account for the observed warming trend that is commonly associated with global warming, but they're pretty relevant to the timing of glaciation periods. Can't post any links yet, but wikipedia should have a somewhat ok article on it.

Thanks; now that I know what it's called, I can research it on my own.

 

[shanek]

It's not true that it's cooling in the southern hemisphere. It's warming, but at a slower rate than the NH. Some areas, such as parts of Antarctica have been cooling, however. See here.

In any case, the Earth's precession cycles have a period of about 20 000 years, which is far too slow to be causing the current climate changes. See this graph.

Thanks. More questions:

I notice under "stages of glaciation" that we're in a current peak that seems to follow cyclically with what's been going on before. A lot of GW people make a big deal about glaciers in Greenland and Antarctica melting and being lost; but shouldn't we expect that given this particular graph?

Is there any way to see better-resolved data for this graph over the last, say, 1000 years?

 

[a_unique_person]

Water vapour is not a forcing. It is a result of temperature change.

 

[Brian the Snail]

Thanks! So nice to have a straight rational answer on this issue.

I have some more questions about this site then:

About this graphic: http://www.globalwarmingart.com/wiki/Image:IPCC_Radiative_Forcings_gif

It says that solar (which I would think is a very significant variable; I've been outside in an eclipse, after all) forcing is least understood. "Very low" scientific understanding, and all the way to the right of the graph. If that's the case, I would expect the error range for solar to be rather high. How much is actually known about solar effects?

Of course the sun is vitally important, but it's the change in its luminosity which is important for driving changes in the climate. As I said above, the sun's irradiance has been measured directly over the past 30 years, and just shows a change over each solar cycle without any significant trend. So it can't really be a significant factor in the warming over recent decades.

Before that, the sun's luminosity can only be inferred only indirectly by measures of the sun's activity, such as sunspot number or relative concentrations of isotopes of beryllium or carbon. So the knowledge is less certain, which is why the understanding was "very low" in the IPCC Third Assessment Report, where the figure you linked to is from. In the latest IPCC report (4th Assessment) this has been upgraded to "low", as seen in the figure that Shabaz posted above.

The error bars for each forcing are also included in the graph, so the solar contribution could well be larger by a factor of two. It's still a long way from rivaling greenhouse gases though.

Also, same question as above: where is water vapor? How much of an effect does it have, and why is it not included in the charts?

Water vapour is classed as a "feedback", not a forcing, since its concentration responds to changes in temperature, which in turn drives further temperature increases.

This article explains it in more detail.

I thought volcanoes put CO2 into the atmosphere? Or do they also put out enough sulfate aerosols to counteract it?

Volcanoes do emit CO2 as well as aerosols, but the aerosols more than counteract the CO2, leading to a net cooling for a few years after an eruption.

 

[Shabaz]

Water vapour is not a forcing. It is a result of temperature change.

From what I understand, it is a potent feedback mechanism though (i.e. warmer air can hold more water vapour, more water vapour can make for warmer air, which can hold more vapour, etc.). And it is mentioned as such in the AR4 SPM. So if shanek would want to read up on water vapour's effect on the warming trend, its feedback properties are probably what are of interest in that context.

About this graphic

Just one small thing; that's I believe the radiative forcings breakdown from the IPCC Third Assesment Report from 2001. I posted what is essentially the same chart, but from the Fourth Assesment Report to be released in 2007. So you might want to use that one, or just look up the chart yourself in the AR4 Summary for Policymakers that was released last month (should be on the IPCC frontpage).

 

[CapelDodger]

Thanks. More questions:

I notice under "stages of glaciation" that we're in a current peak that seems to follow cyclically with what's been going on before. A lot of GW people make a big deal about glaciers in Greenland and Antarctica melting and being lost; but shouldn't we expect that given this particular graph?

We're at a peak (or physical minimum), still climbing, and at an increasing rate. Not what one would expect at this stage in the cycle. But then again, there hasn't been 380ppm of CO2 in the atmosphere until very recently so it's hardly surprising that this cycle is bucking the trend.

The Greenland and Antarctic ice-caps haven't melted away for millions of years, so if they do it will be unexpected. The glaciers and ice-sheets come and go, of course. And the oceans go up and down in tandem.

You will not find salvation in the past, because the past presents no examples. These are strange times we're living in.