Global warming

Apparently, it’s real. Apparently, it was shown that “greenhouse” gases, chiefly CO2, cuses it. I also remember that the Earth’s climate never was stable (like all things in nature), although the changes were slow or fast.
Is the last Ice period still here or did it end? My question is: is Earth still warming? Or cooling? Is it possible to estimate the average temperature at the peak of the last Ice period, from the lowest lattitudes of glaciers at that time? Is it possible to estimate the temperature gradient?
I hear a lot of “greenhouse” effect and nothing about natural warming. So, could it be that we measure the combined effect and it’s all ascribed to pollution?

Not CO², there are much worse things and one of the worst that I’ve heard of is methane, yep, cow farts… You might be confusing CO with CO². There are some floro-carbons (sp) that are way bad too.

Ice ages are not caused by the earth cooling or warming I hear, but by the atmosphere changing, why ‘they’ say global warming is beyound me.

This is all BS, I just made it up…

Geologically, yes, we are still in an Ice Age (defined by having polar ice caps). AFAIK, we are still warming up from the last one.

And there’s the rub. You have to look at very long-term trends. There’s a LOT of short-term fluctuation. If the high temperature on May 1 is 60 degrees, and on May 2 it’s 59, you can’t extrapolate and predict blizzards in June – it’s just a normal little dip on the way to summer. Similarly, if this year was a little warmer than last year, again it doesn’t necessarily mean anything. You have to look at several decades, even centuries, worth of data before you can be sure you are seeing a real trend. And, of course, the records in a lot of places aren’t so good going back that far.

From what I hear (and, for the record, I’ve worked in the natural sciences for the last twleve years, working with people who know – and do – the science, but who tend to err a little on the alarmist side), most scientists do indeed agree that the Earth is getting warmer, and many believe that man-made greenhouse gasses have indeed contributed to this in the past century or two. But the extent to which human activity is to blame (vs. the extent to which this is a normal, natural event) is a topic of intense speculation. No one was around to keep records during previous Ice Ages, so we have no baseline for comparison.

The greenhouse effect is a natural process, without it life as we know it would not exist. This is a proven process, it occurs on other planets as well as the Earth. Certain gases in the atmosphere trap heat, keeping the Earth at a livable (for us) temperature.

Global warming is more accurately described as global climate change (not all places are expected to see temperature increase, there will probably also be changes in storm activity, annual precipitation etc) and is caused by “the enhanced” greenhouse effect. This is because concentrations of the gases in the atmosphere that trap heat are increasing. Thses include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) HFCs, PFcs and sulfur hexafluoride (SF6).

Fairly extensive records of temperature and atmospheric CO2 levels exist from methods suchs as tree bores, pollen records and ice cores.

There is extensive information about this on the web. Try:
the EPA

ASD, I understand more or less about global warming. My question is: is it all due to man’s activity, as the Green party claims, or is it, at least partly, natural, due to increase in solar activity, and/or internal geothermal activity, etc. Can the rate of earth “deglacierzation” during the past 10,000 years be an indicator of it? Have it stopped? Etc.?

Life as we know it would not exist without the Greenhouse Effect? Perhaps… but what life is there on Venus, where the Greenhouse Effect has gone awry?

The OP’s difficult to answer. Good temperature data exist for maybe the last 200 years, and average temperatures have risen in the long-term, with fluctuations all over the place. As mentioned, we have good measurement of carbon dioxide levels in the past. The temperature has risen, but it has also done this before. Most available objective measurements of increased temperature do seem to offer some correlation with increasing industrialization, but hard to know if this is independent.

The problem with enviromental issues such as these is that many companies have a vested interest not to spend money on change. Big corporations form and fund groups with names like “Citizens For A Green Economy” or what-have-you who demand proof of changes before any action is taken. In this case, such proof is probably impossible.

A reasonable approach is to ask what is the cost of not taking action on issues such as the Greenhouse Effect, the ozone layer, etc. in the absence of proof. I do believe the Ottawa Accord to reduce carbon dioxide was a good step. I don’t always trust big corporation’s goodwill regarding the environment, since I think their record in the past has been pretty spotty.

In summary, although there is lots of short-term fluctuation, the temperature has been rising and greenhouse gases certainly contribute to this. However there is a natural fluctuation in carbon dioxide and I don’t think the Green Party is correct in attributing all the change to man. But I do agree that actions need be taken.

The Greenhouse Effect is a fact (certain gases in the atmosphere retain heat…its helps keep us warm and has turned Venus into an inferno). Human-induced Global Warming is a topic under debate. Many scientists are convinced that it is happening (human-induced, that is), but there is no absolute proof. Nor is there likely to be. Weather & climate are complex systems (difficult to predict) and we don’t have perfect long-term data. It’s a weight of evidence kind of thing.

Many scientists do see a warming trend, but the percent contribution from natural climate changes vs. human activity is uncertain.

Increased solar activity is, IMHO, an unlikely source. It goes though 11-year high/low cycles and we just happen to be at the peak of the high period. But just a few years of small scale solar changes is not enough to send the climate out of control considering that the sun has been nice and stable for billions of years. It does grow hotter with age, but this is unlikely to become a problem for a couple hundred million years from now.

I’m still weighing the evidence for myself, but so far my 2 cents (IMHO) are as follows…
The Greenhouse Effect is real. Global Warming is a possibility. Most scientists researching this topic are seeing increasing tempatures over time. Like everything else in life, it’s probably a mix of causes. Some natural and some human-induced (since we are increasing the concentration of greenhouse gases in the atmosphere as determined from ice core data, etc.). The amount of human input is uncertain and the future outcome is uncertain. Since this has the potential to adversely affect us (either just a little or in the extreme), we should proceed with caution…keep researching and try to reduce emissions until we figure things out better. People who say they are absolutely sure it’s happening or absolutely sure it’s not, are not thinking this through and may be pushing some other agenda.

I do not doubt the “greenhouse effect” per se. I am just amazed that some people (Al Gore is a good example) want to ban the internal combustion engine. It looks, that a good volcanic eruption emits more into the atmosphere than all cars. I think we should limit emissions, I do not like the stink in the streets myself, but should we spend zillion fighting windmills?

The other question is: is it possible to calculate the “iceline”, i.e. the lowermost lattitude of ice caps, at given average temperature? With a computer model? Based on satellite data? And then “check” it, using fossil data pertaining to 10,000 years ago? I understand the complexity of that: even averaging 100 years of temperatures may be “short term” in geological sense. But is anything even tried? I hear a lot of blubber about man-made air pollution but nothing about the above. Just finished the Net search. Tons of pages about “emissions”, “air pollution”,etc., but nothing about natural warming. It looks like nothing is known.

I don’t have the info you’re asking for on-hand…hopefully someone else here does. But as to your above statement, I’ll just say that the “blubber” is only what makes it to the media’s attention. The real science is behind the scenes. Natural sources and sinks of greenhouse gases, changes in the albeido of the Earth, solar activity, etc. are considered too, AFAIK. (at least I hope so!)

Another variable to throw into the mix is heating the atmosphere the simple way: burning things. I’ve read arguments that the amount of energy produced by the creation of heat by simply releasing stored energy (e.g. fossil fuel burning, nuclear reactions, etc.) may have (or be approaching a level where it will have) an impact on global temperatures. The trouble with this is that it’s a lot more painful to lower total energy use than to reduce emissions…

peace, going back to your OP, it seems that you have a number of questions, some of which are more easily answered than others. Here’s my take:

Q: Is the last Ice period still here, or did it end? … is the Earth still warming? Or cooling?

A: At the moment, geologists consider the earth to be in the midst of an interglacial period - ice sheets do still exist at higher latitudes, and given the appropriate conditions (we we don’t quite know yet, btw) they could presumably advance again. During the present Ice Age, ice sheets have been periodically advancing down from the poles and then retreating again for the past 1.8 million years. Other ice ages have taken place at various times in Earth’s history, alternating with warm intervals when we think that even the polar ice caps were either miniscule or absent.

Data gathered from the last few centuries are reliable to varying degrees, but on the whole it appears that the Earth has in fact been warming up a bit. The debate centers on just how much of that warming is due to human activities such as burning fossil fuels. I don’t think any geoscientist out there would be willing to argue that the current warming trend is due solely to human activity. After all, we know that one of the more recent interglacial intervals (approx. 125,000-140,000 years ago) was even warmer than the present, and our human ancestors were most definitely not doing much by way of fossil fuel burning back then. :wink: I haven’t paid much attention to the Green Party platform in this past election, but if they’re saying that the current warming trend is solely the result of human activity, that’s politics talking - NOT science.
Q: Is it possible to estimate the average temperature at the peak of the last Ice period, from the lowest lattitudes of glaciers at that time? Is it possible to estimate the temperature gradient?

A: A ton of temperature estimates have been made for the past 2 million years or so, but not from indicators of maximum ice sheet advance. Most are estimates of sea surface temperature, which come from the study of oxygen isotope ratios in the calcite shells of marine plankton. (The entire field of paleoceanography is built on such studies.) Reliable estimates of land temperatures are somewhat more difficult to obtain, but can be derived from things like changes in vegetation type and measurements of noble gas ratios in groundwater.

There are computer models that can use the observational data to reconstruct a portrait of global climate trends (including parameters such as temperature, precipitation, wind patterns, etc.). These are imperfect tools at the moment, because we are far from understanding all the complexities of how climate works on this world, but they are still useful tools for trying to understand broader climatic trends. (Incidentally, climate modelers use paleoclimatic conditions on a regular basis to help “tune” the models, so that model output more realistically represents the observations.)

Later in this thread, peace, you mention the effects of volcanic eruptions. To clarify: very large volcanic eruptions have the potential to COOL climate, not warm it, because of the aerosolized sulfur dioxide that gets injected into the stratosphere (where it may persist for some years). The aerosol particles act to reflect incoming solar radiation, and so contribute to an overall cooling of the climate. Such effects are temporary, though, even on human time scales.

Please understand that there is a helluva lot of work going on right now to understand how the climate can change, and what the driving forces might be. I just took a look at my university library’s list of journals and found a whole bunch almost exclusively devoted to past and present climate change and climate processes (e.g. Atmospheric Research; Climate Dynamics; Climate Change; Climate Modelling; Global and Planetary Change; Global Environmental Change; Journal of Climate; Journal of Geophysical Research - Atmospheres; Meteorology and Atmospheric Physics; Palaeogeography, Palaeoclimatology, Palaeoecology), not to mention numerous other journals that may also feature climate-related research papers from time to time (like Science or Nature). In this instance, the Internet is much more likely to drop you off at a politically-oriented site rather than a science-based site.

If you’re interested in understanding some more about what we know of Earth’s climate trends over the last 2 million years or so, and the various techniques used to gather and interpret data, I would highly recommend R.S. Bradley’s Quaternary Paleoclimatology. It won’t give you answers about future climate, but you will get a much better feel for the data that folks are using to back their respective arguments.

Q:In this instance, the Internet is much more likely to drop you off at a politically-oriented site rather than a science-based site.

I am afraid that it actually happened. I am sure, that there are cool heads in the Green Party (I used “Party” inapproprietly, “green movement” would be a more appropriate term), but I was so surprised: everything was about human activity. Thanh you, Fillet, for educating me.
And, finally, about volcanos: I knew about possible cooling
effect of volcanic eruptions, due to particulate matter emissions and things you mentioned. I referred to the gaseous phase. Among tons of emitted gases some must have “greenhouse” properties.

Big picture view: the average temp of earth is a sine wave (period of 100 years or so), and we’re just on the upswing.

    /\        /\        /\
   /  \      /  \      *  \
  /    \    /    \    /    \
 /      \  /      \  /      \
/        \/        \/       and so on...


It’s actually a curve, not straight lines, but it’s as good as I can do in text.

You’re welcome, peace.

Re volcanoes: volcanoes can and do emit CO2 (amplifies warming), as well as sulfur dioxide and particulates (dampens warming if injected into the stratosphere). Large volcanoes prone to explosive* eruptions, like Tambora or Krakatau in Indonesia, have an overall cooling impact, though, because the short-term cooling effects of the sulfur dioxide and ash particles overwhelm the warming contribution of CO2.

Volcanoes that have less explosive eruptions, like Mauna Kea, are more likely to contribute to some long-term warming largely precisely because their eruptions don’t inject sulfur dioxide or ash into the stratosphere (no cooling effects to counterbalance the CO2). However, the addition of volcanic CO2 does not appear to occur normally at a rate that would make a significant difference on human time scales. On geologic time scales, that CO2 would eventually be drawn out of the atmosphere and buried in organic matter or limestones as part of the carbon cycle.

Gunslinger: I like your sine wave, but the 100-year period doesn’t quite fit the existing data. :slight_smile:

  • By explosive eruptions, I mean that the lava erupted is viscous enough to retain much of its dissolved gases until the lava is exposed to the relatively reduced pressure of the atmosphere.