Excellent explanations. So, in lay man terms this is what I understand. Please correct if I am wrong.
1. There are very slight mean temp that is rising
The temperature rise from pre-industrial to present conditions is about 0.8 degrees C (or 0.8 K). That is large on global-scale, decadal-scale variability so we can see the warming signal clearly, and is in line with what is happening with sea level rise, glacier retreat, biological responses, etc. I noted, for perspective in a previous post that a temperature reduction of ~4 C will give you an ice age; the last time temperatures were about 2-3 C higher was during the Pliocene millions of years ago with subtantially higher sea levels. The rise is pretty significant, and you get about 3 C will a doubling of atmospheric CO2 at equilibrium.
2. At say 0.2 degree rise, the total BTU input is a lot.
We weren't discussing BTU, we were discussing radiative transfer and radiative forcing. With addition of greenhouse gases, you reduce the outgoing longwave radiation (OLR), and turn up atmospheric absorption. You and milkweed need to throw out whatever idea of radiative forcing you are using, and use the one at .grida.no/climate/ipcc_tar/wg1/214.htm (yes, throw in http and www beforehand, this is rather lame but I'm not at the post number to put links up). Secondly, the "change" is not as trivial as has been implied before. The radiative forcing for a doubling of CO2 is easily calculated to be ~4 W/m^2 and this is not simply "added to" the LW absorption of 150 W/m^2 (i.e. the "new" LW absorption is not 154 W/m^2, probably around 170 W/m^2 with 2x CO2). The change of the initial 4 W/m^2 forcing and the 20 W/m^2 at equilibrium is from LW feedbacks (like water vapor). So, milkweed was wrong in the first place to say the change was small (the temperature or the radiative forcing).
3. This could be natural change for Planet Earth due to solar radiation and Solar movement in Milky way and other cycles.
But right now, there is no significant trend in solar radiation. Next, different causes for climate change generally show different "fingerprints." For example, increases in solar radiation would warm the stratosphere, and increases of CO2 would cool the stratosphere. Other differences show up with latitude and/or altitude, and the current trends are consistent with those from greenhouse gases. This has repeatedly demonstrated to be successfully predictive as well as explanatory with high confidence. If you want to argue for another mechanism, you'll need to show all the current data is wrong, and show new data showing changes in natural variation are sufficinetly stronger, or that possible-but-unproven signals exist in the climate system which are causing the warming, and that all have the same fingerprints as greenhouse gases. Moreover, even if there was a solar signal, adding CO2 would only amplify that, so if you want to argue against AGW you'd further need to show why the CO2 physics is wrong.
4. We do not know what the natural change looked like in the past
This is not defensible. There are uncertanties as you go back in time, but the picture is there. We know that there are glacial-interglacial cycles over the last million years, we know it was much hotter 55 million years ago, we know the Earth entered a snowball state and froze over down to tropical latitudes around 700 million years ago. As you go back on shorter scales, like a few hundred years agom or a few thousand years ago, there are still error bars but a very clear idea on global climate.
5. Human society is pouring in a lot of CO2 from Fossil burning and cutting down CO2 moppers - the plants.
Yes
6. It is possible we could come out unscathed as the planet could heat balance itself to a new norm.
It is hard to think of any situation where you can't get some winners and some losers, or some people just don't care. This also depends on how much warming we get, which will depend on how much we continue to burn. It also depends on regional factors. My guess is Russians and Canadians won't complain too much. Africans, people in south an central America, areas of Asia or Australia won't be too happy. The millions of people who depend on big glaciers like in the Himalayas won't be too happy. A lot of ecosystems like coral communities won't be too happy, and others will probably benerfit. In terms of evolution though, out rate of warming is too fast for widespread adaptation, and aside from major extinction events or abrupt climate changes (which did have big ecological impacts), climate changes generally took a long time too complete. The ice age cycles I mentioned occurred on thousands-of-year timescales, not rapid changes on decades. Information on global and regional climate projections can be found in the IPCC working group 1 2007 report, and report on impacts and adaptation in working group 2.
7. If we add to the planet's change in amplitude, we could cause a positive feedback and the planet may not be able to balance itself. It is like when you get a feedback to a mike from the speakers and the system oscillates.
The planet will eventually reach *radiative equilibrium* (feedbacks included). But to achieve a new equilibrium, you need to raise the temperature. This depends a lot on how much, and how fast we put greenhouse gases in the atmosphere, and measures we take to stop.
8. If the runaway reaction occurs, we are doomed.
If you are talking about a "runaway greenhouse effect" we would be doomed, but that is hardly possible on Earth, and nothing like our current situation can give us a "runaway effect." That is not to say the warming can't be bad, but a runaway effect is like that on Venus. However, some things like ice loss could be considered runaway in that once they are pushed past a certain threshold, they may be unable to return to initial conditions. For example, if you melt the entire arctic, and then return the global temperature to pre-industrial conditions, the arctic is not going to magically come back.
Then question comes is that are we too late?
We are not too late for "disaster." This is very hard to define, and will probably change depending on who you talk to. Personally, I would say a change of temperature of 2 degrees would be out of my comfort zone. If we continue to emit fossil fuels at business-as-usual rates, then, by 2100 I would say, we will be "too late."
Do we know what percentage change we are introducing in relation to the Earth's normal changes. The reason is nature has a great reserve in its ability to handle change. It is like human body temperature regulation. We can handle 110 degrees, but may not 120 degrees from a 70 degree comfort zone. So are we pushing the temp regulation too far for the planet?
The Earth isn't going anywhere, and has endured much worse. The concern is macro-scale life on Earth which has evolved to specific climatic conditions, and the way in which our civilization was built (big populations, very coastal, on islands, etc). As I've said, a lot of species or areas will be fine, and others will suffer quite a bit. Coral reefs which are very important for marine biodiversity, and the economics of tourism are in big threat. Species will a narrow range of conditions in which they can survive, or those on mountains will not be too tolerant to a climate change
