This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.
Objection:
A few glaciers receding today is not proof of Global Warming, glaciers have grown and receded differently in many times and places.
Answer:
But no one claims that melting glaciers are proof of Global Warming. Proof is a mathematical concept. In climate science one needs to look at the balance of evidence and in that light, the above data is just one piece of evidence that is consistent with Global Warming.
So what do we find if we look to the other aspects of the cryosphere?. It turns out what we find is lots more evidence that is indicative of world wide and sustained temperature increases:
- Sea ice in the arctic is reaching new record declines as the year 2006 continues the pattern of sharply decreasing Arctic sea ice.
- Recent measurements by NASA have found that Greenland's massive ice sheet has been losing nearly 100 gigatons of ice annually in recent years.
- Glaciers in Greenland are receding and calving at record rates
- Ancient permafrost is also thawing, (which represents its own dangers)
And of course, this is all consistent with all the other evidence of warming that there is out there. Clearly we are dealing with much more than a few receding glaciers.
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.
"Glaciers have always grown and receded" was first published here, where you can still find the original comment thread. This updated version is also posted on the Grist website, where additional comments can be found, though the author, Coby Beck, does not monitor or respond there.
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Glacier recession is a suggestion of warming (global? meh). It is not necessarily of a suggestion of anthropogenic warming.
Posted by: Matt | January 31, 2009 11:28 AM
Nice graph. Too bad you're cheating. Why not show the full data? Back to the 1700s? Our current retreat is nothing new in the context of the past two hundred years or so. The trend simply continues. So much for the big bad humans doing it.
Posted by: Duh | March 14, 2009 12:35 AM
Duh, why don't you provide us with this misssing data, back to the 1700's? Because it does not exist of course. There is not enough global coverage prior to the 60's to construct such a graph.
Posted by: coby | March 14, 2009 9:12 AM
Coby, that was the point, you are drawing a massive conclusion from a tiny shred of data. Bad. Unless someone can show evidence that glaciers do not retreat without interference this is not evidence of anything.
As for me I believe this planet experienced an ice age, and all those glaciers retreated. Man had nothing to do with it; the planet is better off for it. Also true that some small villages rely on melting glaciers for their precious water. Melting glaciers is therefore good. If they retreat a lot then some villages have to move. Oh, well, they must have done that before, so here goes again.
Posted by: RS | March 24, 2009 3:37 PM
RS, I believe what I said was it is consistent with all the other evidence of warming, so no I did not draw a massive conclusion from a tiny shred of data. Please provide the quote you had in mind.
As for the retreating ice age, check this article. That retreat ended 10-8000 years ago.
Posted by: coby | March 24, 2009 3:43 PM
If you conclude that a tiny shred of evidence is consistent with anything I believe you must give significant weight to that shred.
As for the 10-8000 years ago, what caused that? Seems like growth and retreat has been happening for a long time. And whatever it was that caused the retreat, aren't we pleased?
Posted by: RS | March 24, 2009 4:34 PM
The last glacial period ended because of a combination of orbital forcing, CO2 rising and albedo changes as ice sheets shrank.
Yes, it was fabulous news for me, my apartment might still have been under 2 km of ice.
Posted by: coby | March 24, 2009 4:52 PM
Coby you consistently miss the point that the sea level 18,000 years ago was 400 feet below where it is today! With no human input, the sea level came to its present level (but for about 2-3 feet) about 3000 years ago.
In other words, the sea level is about where it was 30,000 years ago, before the last ice age. Earth cooled, with no human input, then it warmed with no human input.
John
Posted by: John, Ft. Lauderdale | July 28, 2009 9:58 PM
Hi John,
Please see this article:
http://scienceblogs.com/illconsidered/2006/03/global-warming-is-nothing-new.php
BTW, your chronology is a bit off. Going back from 18ky bp you have to get to about 120K yrs before sea levels were as high as today, actually about 4 to 6 metres higher, 30K yr bp it was still very cold!
Posted by: coby | July 28, 2009 10:08 PM
And, of course, before guns were invented, no one died of gunshot wounds, which proves that no one died from machine gun fire in WW I, WW II, Korea, Vietnam, Iraq I, Iraq II ...
Posted by: dhogaza | July 28, 2009 11:13 PM
Come on dhogaza, i can accept a little drift off topic but for christs sake that is just c@#p. If you cant think of anything intelligent to say then say nothing at all.
Anyway guns were invented before the wars of conquest you mentioned above so people could have died from gunshot wounds.
Looks like that "itchin for a fight" needs to be scratched again, consider it scratched ok.
Posted by: crakar14 | July 29, 2009 12:42 AM
crakar, he is trying to make the point that just because X caused Y in the past does not prove that Z is not causing y now.
I make that point a little clearer in this post:
http://scienceblogs.com/illconsidered/2006/01/climate-is-always-changing.php
Posted by: coby | July 29, 2009 8:00 AM
re: Recent measurements by NASA have found that Greenland's massive ice sheet has been losing nearly 100 gigatons of ice annually in recent years.
How long would it take for all the Greenland ice to melt at this rate? My "back of a fag packet" calc came out at approx 22,000 years. But I suspect that must be wrong. Anyone?
Posted by: JackSprat | January 22, 2010 6:58 AM
I don't know but is that even the issue?
As I understand it the problem of Greenland's ice retreat is not the prospect of it all being gone but a whole *lot* of it being gone and the resultant effects on sea levels and the positive feedback of less snow reflecting sunlight back to space. Also Greenland's ice sheet retreat is a gauge of where we are. I mean, Jesus, its melting. Regardless of where we stand on the overall AGW hypothesis, does anyone dispute it?
Posted by: skip | January 22, 2010 8:18 AM
Skip, thanks for your reply.
I guess my question is "is there an issue"? 100 Gigatons sounds awfully impresive, however -
100 Gigatons of ice melting is about 0.00452632% of the total Greenland ice sheet, which will put the sea levels up about 0.0003546 of a metre. (Someone please verify my figures).
And the reduced reflectiveness of this small difference - does it amount to anything?
BTW - I am agnostic regarding AGW, I'm just seeking answers to niggles I have. Thanks
Posted by: JackSprat | January 22, 2010 9:22 AM
Those numbers sound about right - for the recent melt rate. Changing units, that's 0.35 mm/y. Current annual sea level rise is almost 10 times that (about 3mm/y) but more than half is from the expansion of warming water, the rest is from Greenland, Antarctica and other glaciers around the world.
Here's the trouble with 0.3 mm/y from Greenland. A mere decade ago it was basically 0. See http://www.skepticalscience.com/Why-is-Greenlands-ice-loss-accelerating.html (particularly the second graph). That's an accelerating loss. It's accelerating for probably two reasons: (1) It's still getting warmer (2) Greenland is a hollow basin, ringed by mountain ranges, filled with ice. As the outlet glaciers retreat, the area exposed to warming ocean water increases, so the basal melt rate increases, with positive feedback.
So, while I certainly can't guarantee it, the mass loss rate of Greenland could double in another decade, double again in the decade after that, etc. until leveling off at a rate that would melt the whole thing in ~500 years. That would contribute over 1m/century. A slightly different accelerating dynamic is affecting the West Antarctic Ice Sheet. Taking all sources into account, we are likely looking at 1.4m sea level rise by 2100, with 2-3m/century for several centuries after that. That's if we don't get our act together on mitigation.
1.4 meters is huge. It doesn't seem that big if you live near a rocky shore, or don't live near a shore at all, but the first 1 meter of sea level rise will wipe out half the agriculture in Bangladesh, and have similar effects on other low coastlines around the world. The population of Bangladesh is 160 million.
Posted by: GFW | January 22, 2010 9:51 AM
GFW - thanks for the comprehensive reply. I'll checkout the link etc over the next few days.
Posted by: JackSprat | January 23, 2010 4:18 AM