A historical perspective on climate change

[bik0]

Temperatures have gone up and down for hundreds of millions of years. Humans have only had an impact for the last hundred years. How can we explain warming periods prior to 1900? Solar activity, ocean currents etc.? How can we be so sure that those same warming factors are not at play today? How can we point to CO2 as the ONLY explanation when warming and cooling is a natural phenomenon (prior to 1900)? When looking at temperature change over long periods of time, the warming this century is not that out of the ordinary.

http://www.foresight.org/nanodot/?p=3553

Temperatures for the last 500 yrs...

last 1000 yrs...

last 4000 yrs...

last 10,000 yrs...

last 12,000 yrs...

last 50,000 yrs...

last 400,000 years...

[baldguy]

1. And the temp increase in the last 150 yrs is due eclusivly to human industrial activity.

[bik0]

2. How do you explain warming prior to 1850?

There have been many, many periods of warming prior to 1850.

[mix]

5. Non-anthropogenic forces are most likely the causes

of pre-1800 periods of warming...everything changes, however, with the Industrial Revolution...the spike in population growth and global dependency on fossil fuels; these phenomena are driving climate change today.

[happyslug]

39. England started to burn Coal in the 1300s

What I mean by burning coal ACTUALLY USING COAL IN A WIDESPREAD MATTER. We Know this for the English Parliament actually passed a law AGAINST burning coal in the 1400s do to the soot form burning coal (the law was ignored). That release of Carbon MAY have been enough to increase world wide temperatures by the small amounts noted before about 1850. People forget the reason Watt invented the Steam Engine was to pump out water from Coal mines already in widespread use by the early 1700s. The rest of Europe was NOT that far behind (And neither was Japan, which has coal in its most northernmost island, China, Russia and India. With the US going into extensive coal mining from about 1800 onward).

In fact one of my favorite "theories" is that the "Little Ice Age" was the start of a new Ice Age but the advent of extensive burning of Coal stopped it in its track. We are in a period where it should be getting COLDER not WARMER (According to some students of the Ice Age). The best explanation of why not may be that we have been releasing to much carbon for CENTURIES.

Please note the reason we are facing RAPID Climate Change is that the use of Coal (and other Fossil fuels) have increased dramatically since about the 1850s (For example it was in the 1870 Census of the United State that you first find that Machines, mostly run on fossil fuels, through some were run by wood, were providing more power then we were getting from man and animal power). Just because the amount of Carbon being released before 1850 is minor compared to the Carbon being released since the 1850s does NOT mean it was NOT having an affect. Human beings have been having an effect on the environment since at least the last 100,000 years. Unlike any other animal we can release carbon any time we want to through the use of FIRE. With Fire we can direct where animals go, what grows in an area, etc (On the stone age level) with the invention of Farming and the use of Metals (Both of which make extensive use of fire) we could affect the environment to an even greater degree.

My point is MAN, by himself could have (and more likely then not did) affected the climate for much of the world over the last 50-100,000 years, with an increasing level over the last 1000 years. Even the small amount of carbon released prior 1850 may have been enough to increase the temperature in the amounts estimated for the last 100 years. Something think of, remember the old Military saying "The horse was lost to the want of a nail, the Charge was lost through the lost of a horse, the Battle was lost through the lost of a Charge, the Nation was lost with the lost of the Battle. The same with pre-1850 coal burning, minor compared to what is being done today, but may have been enough to stop an ice age from starting and to increase the temperatures for the period over the last 1000 years.

[baldguy]

10. Natural sources of CO2, fluxuations on solar activity - which don't explain the recent increses.

Why are you posting climate change data from a site devoted to molecular nanotechnology? Why don't you look at what actual climate scientists & researchers say?

http://www.sciencemag.org/cgi/content/abstract/289/5477/270

Causes of Climate Change Over the Past 1000 Years

Thomas J. Crowley

Recent reconstructions of Northern Hemisphere temperatures and climate forcing over the past 1000 years allow the warming of the 20th century to be placed within a historical context and various mechanisms of climate change to be tested. Comparisons of observations with simulations from an energy balance climate model indicate that as much as 41 to 64% of preanthropogenic (pre-1850) decadal-scale temperature variations was due to changes in solar irradiance and volcanism. Removal of the forced response from reconstructed temperature time series yields residuals that show similar variability to those of control runs of coupled models, thereby lending support to the models' value as estimates of low-frequency variability in the climate system. Removal of all forcing except greenhouse gases from the ~1000-year time series results in a residual with a very large late-20th-century warming that closely agrees with the response predicted from greenhouse gas forcing. The combination of a unique level of temperature increase in the late 20th century and improved constraints on the role of natural variability provides further evidence that the greenhouse effect has already established itself above the level of natural variability in the climate system. A 21st-century global warming projection far exceeds the natural variability of the past 1000 years and is greater than the best estimate of global temperature change for the last interglacial.

[bhikkhu]

29. Complicated - but there are many good books on the Ice Ages and so forth

I just finished going through my library's shelf of them.

Briefly, there is both a long and a short-term astronomical cycle, there are variations in solar output, there are variations caused by wandering positions of continents over time, there have been many periods of volcanism, and aspects of life on earth causing changes to the balance of atmospheric gases and the albedo of the surface.

I think the big current issue is that our 29 billion tons a year of CO2 emissions are close to outweighing any natural variability.

[mix]

3. and to the enormous spike in the world's population due to the Industrial Revolution

[TxRider]

7. Now that is one scary graph

And the oil trend is going to reverse, will the population trend go with it?

[GliderGuider]

24. I think it will

I was the original author of that graph. It's from my article Population, The Elephant in the Room. In the article I make a case for population following the oil supply, and put out my personal belief that the sustainable human population in the absence of fossil fuels is around one billion. I look at what it would mean to the human experience to arrive at that number involuntarily over the next 75 years. It's not a pretty picture, and lots of people object to it for a variety of reasons. I still think we'll be faced with something like it during the next century.

[bik0]

8. Warming has occured prior to population explosion

Warming happened when the world population was only a few thousand Homo Sapiens living on the plains of Africa.

[mix]

11. I'm sure it did. Today's world is different.

More people and fossil fuel dependency on a global-scale mean a warmer planet, and perhaps irreversible damage to our habitat world-wide.

This is a very different scenario than pre-1800 warming trends.

[TxRider]

6. Not even the IPCC says that.

[notesdev]

4. An inconvenient truth, indeed

which the Warmers immediately jump on and unrec into oblivion, lest anyone see the facts.

[Nihil]

18. Not really ...

... I'd quite like as many people as possible to see the graph
posted in reply #3 as it works like a hammer to the head for
getting people's attention and most of the responses here are
informative attempts to explain the situation to "our new friend".
:shrug:

[notesdev]

19. Looks like a diversion to me

OP is showing temperature graphs and the graph in #3 shows two completely different data sets.

Correlation is not causation, statistics 101.

[Nihil]

27. A straight line would look "like a diversion" to you. (n/t)

:eyes:

[NYC_SKP]

9. Several reliable websites, including US government websites Pre-Obama support the science.

I'm not going to take the time to provide links, but I'll do this much.

The graphs you post show temps only. The graphs of interest combine CO2 levels with temps, like this one:



The challenge for climate change skeptics is to debunk the correlation, and they cannot.

What do you say to that?

[bik0]

12. Does CO2 cause warming or is it the other way around?

Most scientists agree that rising CO2 levels come AFTER warming.

[depakid]

13. That's called a positive feedback loop- and it compounds the problem

dramatically.

[NYC_SKP]

14. Do you have a link for the claim that CO2 levels come AFTER warming?

I have not read that claim.

What is not in question is that CO2, methane, and water vapor are among the various greenhouse gasses.

And it is agreed that these interact with incoming and outgoing radiation in such a way at to retain more or less energy and thus impact temperatures.

And it is agreed that activities such as the burning of fossil fuels, cement production, and other human activities are increasing the concentrations of CO2 in measurable ways.

CO2 traps heat energy ---> We are increasing CO2 levels ---> the more we release, the warmer it will become.

So, even if it's somehow true that warming occurs BEFORE CO2 increases, it doesn't make our further release of CO2 any less dangerous.

And it matters little if we were going to be in a warming trend anyway.

If we were, we certainly don't need to exacerbate it.

[baldguy]

16. I'm sure the National Association of Oil & Coal Producers has some hard data on that.

:eyes:

[bik0]

17. "the CO2 increase lagged Antarctic deglacial warming by 800 ± 200 years"

From Science Magazine...

The analysis of air bubbles from ice cores has yielded a precise record of atmospheric greenhouse gas concentrations, but the timing of changes in these gases with respect to temperature is not accurately known because of uncertainty in the gas age-ice age difference. We have measured the isotopic composition of argon in air bubbles in the Vostok core during Termination III (~240,000 years before the present). This record most likely reflects the temperature and accumulation change, although the mechanism remains unclear. The sequence of events during Termination III suggests that the CO2 increase lagged Antarctic deglacial warming by 800 ± 200 years and preceded the Northern Hemisphere deglaciation.

http://www.sciencemag.org/cgi/content/abstract/299/5613/1728

[bik0]

20. If CO2 lags warming, how can it CAUSE warming?

Will someone please explain.

As someone else stated already... correlation does not necessarily mean causation.

[TxRider]

22. It doesn't cause all the warming, the sun does that,.

It does cause a feedback to accelerate the warming though.

As can be shown by the steeper warming angles in the graph. It also cools with high c02 levels, but as you can see the c02 helps keep it warmer longer as the cooling trend in the graph shows.

As well regardless of what we do, in 80,000 years half of the northern continent will be covered in ice again.

[NickB79]

31. Rest a ball at the top of a hill and give it a push

After the ball starts rolling, it accelerates on it's own. The intial push gave it the energy to start, but positive feedback from gravity did the rest.

In the past, a slight increase in global temperatures from a natural cause (say, the sun increased in output a fraction of a percent) got the temperature ball rolling, adding a fraction of a degree of warming to the planet. The initial warming thawed permafrost, releasing CO2, which helped add another fraction of a degree. That melted MORE permafrost, added MORE CO2, and caused even MORE warming. Soon that ball is rolling fast, far faster than the small initial impulse that started it off.

Today, there doesn't appear to be any natural impulse to account for the warming we've seen in the past century. In fact, we should actually be in a cooling trend based on what we know of natural climate cycles: http://www.scientificamerican.com/article.cfm?id=global-warming-reverses-arctic-cooling

And that is the clincher: if you want to argue that what we are seeing is simply part of the natural cycle of the global climate rather than human-initiated, we should be seeing a measurable DROP in global temperatures, not an increase.

[Viking12]

23. Convenient how you overlook the 2nd half of the sentence...

preceded the Northern Hemisphere deglaciation.

[Viking12]

15. All you questions are answered here

http://www.realclimate.org/index.php/archives/2004/12/co2-in-ice-cores/

[TxRider]

21. 2 things

All scientists agree higher temps will mean higher C02. Correlation does not equal causation.

C02 is higher in warmer phases due to many reasons, ocean outgassing, drastically higher vegetation levels etc.

This is also shown clearly in the CO2 lags temperature both in increasing and decreasing trends.

The effect of C02 is shown in slowing the cooling trend, and increasing the rate in the warming trend.

The difference in the slope in the graph between warming and cooling is the greenhouse effect.

To say C02 is responsible for the warming is utter nonsense. It is only a feedback to help it happen faster, and likely makes the peak higher.

[GliderGuider]

25. The problem with this view is that it ignores human action entitrely.

CO2 rise can only lag temperature rise in situations where the CO2 is operating initially as a feedback mechanism. In this case the original CO2 release is produced by an endogenous temperature increase. Here is that chain of events:

Temperature starts up due to rising solar input, CO2 is released (due to outgassing etc.), temperature rises due to the increased Greenhouse Effect, more CO2 is released, temperature rises faster, more CO2 is released, etc. This keeps going until a new equilibrium is reached.

However, there are other ways CO2 can be released. In the current situation, the first term of that chain of events is missing. It now starts at "CO2 is released" but this is due to the burning of fossil fuels rather than outgassing. Basically humans take care of the initial outgassing by burning FF. The rest of the chain of events remains unaffected. The chain of events that describes the current situation looks like this:

CO2 is released (due to burning fossil fuels), temperature rises due to the increased Greenhouse Effect, more CO2 is released, temperature rises faster, more CO2 is released, etc.

To invalidate this perspective you'd have to make the case that the CO2 released by burning FF has no greenhouse effect. That might be hard to do.

[TxRider]

26. Of course it does, that's the point.

That clearly even though C02 lags in both heating and cooling, it's effect is apparent in the cooling phase in the slowing of the cooling phase starting with high C02 levels.

This is all without human effect, to show the effect C02 has.

Adding in extra C02 from fossil fuels would simply magnify that measurable effect. Even faster warming, higher peak temp, and slower cooling in the glaciation cooling phase.

Or so the theory goes.

The real debate is in how much of the effect is directly related to C02, the climates sensitivity to C02 vs other gasses and effects in a chaotic system. The possible range for that sensitivity value in science is a bit wide at present.

[NickB79]

32. Ocean outgassing is definitely NOT happening

How do we know? Because oceans around the globe are becoming more acidic due to CO2 diffusing INTO them, not outgassing from them. If the oceans were venting CO2, they would be becoming more basic. What we are seeing, however, is the exact opposite of that.

[kristopher]

34. Mmmm, not really.

That view is based on data from very limited geographic sampling. You cannot predict the overall activity in the oceans from such a sample.

Also, the outgassing I think he is referring to is methane. And we have *confirmed* physical observations that such releases are indeed occurring.

[NickB79]

37. Uh huh

http://news.bbc.co.uk/2/hi/science/nature/8411135.stm

"Acidification of the oceans is a major threat to marine life and humanity's food supply, Hilary Benn is to warn as the UN climate summit resumes.
The UK environment secretary will say that acidification provides a "powerful incentive" to cut carbon emissions.
Ocean chemistry is changing because water absorbs extra CO2 from the air."


If you question the science behind ocean acidification research, could you explain how the oceans could absorb tens of billions of tons of CO2 and NOT see a decrease in pH levels?

[kristopher]

40. I don't "question the science behind ocean acidification research"

And there is nothing to suggest I do. I do question your interpretation of the original remark and the process involved.

There are massive quantities of methane sequestered on the ocean floor by temp/pressure/salinity.
The acidification is occurring in the surface layer of the ocean.
The release of methane hydrates is unrelated to the absorption of CO2 and the consequential acidification from that absorption.
Once the temp/pressure/salinity variables allow the release of the methane, there is going to be hell to pay in the air, on land and sea.

There are observed instances of such methane releases now occurring in the Arctic...

Here is the reference that brought this concern into focus: Ryskin, G., 2003, Methane-driven oceanic eruptions and mass extinctions: Geology, v. 31, p. 741–744.

[TxRider]

41. Not currently maybe

It happens with c02 more when ocean temps cool.

Methane outgasses more when it warms, as well as water vapor which is more of a forcing than c02, we just aren't sure how it feeds back into the system completely.

[joshcryer]

28. Every one of those graphs comes from a *single ice core* and cannot represent a global trend.

So I suggest the title be edited to reflect "Some Historical Perspective on a Greenland Ice Core that is Only Representative of a Small Swath of Land in the Middle of Nowhere." MWP, for instance, on that core, is extremely warm, compared to the other more accurate reconstructions of global temperatures at that time.

What is unsurprising here is that the 50k year trend coincides with orbital actions of the planet. The rest of the graph is simply innuendo.

Oh, and just so we're clear, no scientist has ever said "CO2 is the only thing causing the warming." All they have determined is that CO2 is a factor that can be shown to be causing the warming.

They are open to legitimate suggestions. PDO, solar variance, cosmic rays, all of those have been debunked. So feel free to think of more innovative reasons.

[bhikkhu]

30. "One data set from one site in Central Greenland"

Its a good set of graphs, (from NOAA: http://www.ncdc.noaa.gov/paleo/metadata/noaa-icecore-2475.html), but if you tried to "prove" global warming with just one data set you'd be laughed out of about any room and peer-reviewed into anonymity. The same goes for "disproving" it.

The basis for the current consensus on global warming is the correlation of hundreds of data sets, put together by hundreds of scientists around the world. You can always raise doubt with just one set, or one selection of data, but if you actually read up on the science behind the current consensus, it gets more solid the more you study.

Which is to say - when they say we need to do things different or we're screwed. it would be a good idea to look at what we can do different.

[joshcryer]

33. HAHA, best part of this ice core? It was taken in 2000. In less than 5 years melt extent will...

...make it impossible to take a sister core *at the same spot*. Fucking beautiful. Disappointing this garbage is coming from the Foresight Institute.

[bhikkhu]

35. They had a plug for nanotech at the end of the article

...as the solution to our problems, along with a half-way decent summary of the graphs.

[muriel_volestrangler]

36. Your data goes up only to 1900 or so

If you look at what happened to temperatures in the area after that, you see they have increased by about 2 degrees centigrade.

Source: http://data.giss.nasa.gov/gistemp/tabledata/ZonAnn.Ts.txt

That gives the anomalies for the latitude 64 degrees north to 90 degrees - roughly central Greenland (if anyone knows of a temperature record for central Greenland in the 20th century, that would be very handy now).

Averaging out the 10 years around 1900, you get an anomaly of about -65 hundreths of a degree. Average the latest 10 years, and you get about +140 hundreths - ie a 2 degree warming.

Plot that on your graphs (you'll have to go to the ones for the last 4000 years or more, since it doesn't fit on the more recent ones) and you'll see that's a very fast increase - the last time there was a more more less continuous increase of that magnitude was between 7197 and 6925 years ago (-31.4 to -28.8) - 2.6 degrees C in 272 years. That's about half the rate of increase for the Arctic we've seen in the last 100 years.

In fact, that last time that the central Greenland temperature increased more than 2 degrees in 100 years was about 11,250 years ago. When the earth was coming out of an ice age. (Precise figures here: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/isotopes/gisp2_temp_accum_alley2000.txt)

  1000 years ago      temperature
          11.258         -35.4609
          11.274         -35.8061
          11.289         -36.3661
          11.307          -36.422
          11.324         -37.7459

[wtmusic]

38. Nonsense. One cherry-picked ice core sample?

Look at a global average and the picture changes dramatically (note 2004 arrow at left)