I've been following most of this discussion and I'm surprised no one has really placed any emphasis on the causation behind global warming or cooling.
GEOPHYSICIST HAT ON
Lets start with a basic lesson in the factors that could
cause the Earth's surface temperatures to change. Forget the graphs and climate change research for a moment because we can all argue until the end of time about different graphs.
The Earth's surface receives heat from one primary source: The Sun. There are other factors (internal radioactive decay, tidal friction, earthquakes) but these contributions are all several orders of magnitude smaller than that of the sun.
A simple diagram:
This is founded on the basic principles of radiation, absorption, reflection and re-radiation used in physics and chemistry. Heat energy is just infrared waves and has the same properties as light. So this diagram is founded on the exact same reason why an apple is red: absorption and reflection. (An apple will also radiate light in a similar way to infrared but light radiation requires much greater energy input). The majority of heat energy that reaches us from the sun is immediately reflected off into space by our atmosphere and only a tiny, tiny amount reaches the surface directly. So, the Earth is warm and comfortable primarily because of radiation and re-radiation of the heat energy as it bounces around between the surface and the different layers of the atmosphere. If there was no atmosphere, then all the Sun's heat energy would hit us directly with no reflection and you would think we would be fried by all the intense heat, but without an atmosphere all the heat would immediately be radiated out without the convenient "bouncing around bit" between the atmosphere-surface duo. Without an atmosphere, the Earth would be chilly (about -18 degrees Celsius globally with fairly significant fluctuations between the night side and the day side).
So lets all agree that we need an atmosphere and we need greenhouse gases to keep the Earth comfortable. Greenhouse gases are defined as compounds in the atmosphere which are particularly adept at absorbing and re-radiating heat.
Now we are left with a few basic cause and effect situations.
A) If we change the amount of heat output by the sun directly while changing no other variables, then the Earth's surface temperature will logically also change. (Possible mechanism: sunspot activity. higher activity=less solar output)
B) If we change the amount of radiation/reflection coming off the Earth directly while changing no other variables, then the Earth's surface temperature will logically also change. (Possible mechanism: change in ice cover = change in albedo effect = change in radiation)
C) If we change the amount of re-radiation coming from the atmosphere directly while changing no other variables, then the Earth's surface temperature will logically also change. (Possible mechanism: change in greenhouse gas concentrations.)
This is a slightly simplified argument but even here we run into situations where all these if/then conditions are operating at the same time, potentially in conflicting ways to cancel each other out. (No wonder climate modeling requires some of the fastest supercomputers ever invented).
Okay, now that we have the cause and effects sorted out we can look at data.
A) Direct Solar Radiation:
We are currently going into the high activity phase of the sunspot cycle which could explain the downward trend in the last year or so with regards to climate change as compared to all the historic high temperatures we kept hitting in the years 2004-2007.
B) Earth radiation/reflection:
Albedo effect of common Earth landscapes:
We are losing sea ice and glacial ice, primarily in the Arctic. Ice and snow reflect anywhere from 3 to 10 times as much solar radiation than water. It creates an ice-albedo feedback loop.
C) Atmosphere Re-Radiation:
Even if some propose that the ocean acts as a carbon sink, no one can deny that greenhouse gas concentrations are rising markedly in the atmosphere.
Conclusion:
Global warming is occurring. All the mechanisms that can cause the Earth's temperature to increase are being activated. I am of the opinion that it is part of a natural cycle as the Earth comes out of the last ice age but this natural cycle is being accelerated by human causes. I don't think it would stop even if humans didn't exist; its natural. The Earth has been a lot warmer than this before and it has been a lot colder than this before (see picture below) and Earth's ecosystems (and even humans) did just fine. So global warming advocates that insist on the coming apocalypse due to catastrophic floods and mass famine need to calm down. And anti-global warming advocates insisting that global warming doesn't exist need to shut up. Even if you don't think it is caused by humans, at least acknowledge that the Earth is warming. I think the world needs to stop fighting about this and simply agree that human caused pollution of any kind is bad and unnatural and detrimental to the health of humans, animals and ecosystems whether it be atmospheric pollution, sewage, garbage or toxic dumping. In the 80s and 90s there was a big focus on recycling and reducing garbage pollution and there was a general consensus that this was a good thing regardless of political stance. Also, before the global warming debate, it was almost self-evident that air pollution was bad and cities like Los Angeles made a united effort to reduce air pollution simply because it's
bad for your personal health. The world's voters and politicians need to wake up and simply realize that pollution is
bad and who gives a rat's ass if it warms the planet or not.
And please stop using graphs that use the last 10 or 20 years to show climate change. Climate change is something that stretches out for centuries or millennia. A ten year graph is like zooming in on your bank account right when you get your pay day without zooming out to realize that you owe a $300,000 mortgage.
GEOPHYSICIST HAT OFF
***I apologize for any errors. This is all a simplification and there are more variables present but I have listed the major ones***
CO2
