Rate of planetary warming follows Newton’s Law of Motion:

A body in motion tends to remain in motion, unless a force acts upon it.

Thus, based on the experiments in our lab, which showed how C02 emissions are on a path of exponential growth, unless we do something fairly drastic, the levels will surpass our ability to change them. After performing the exercises in the three different CO₂ simulators, I’ve concluded that it is a difficult if not impossible task to restrict further global warming to 2 degrees. In fact, it may not be possible to reduce emissions to achieve this goal, for a number of reasons. The primary reason is that there are complex factors, which affect emissions and absorption, such that emissions into the environment are accelerating at a rate where the planet cannot remove the carbon fast enough, so there is an overflow.
An analogy for this is Newton’s first law of motion, where a body in motion tends to remain in motion, i.e. “An object that is at rest will stay at rest unless an unbalanced force acts upon it. An object that is in motion will not change its velocity unless an unbalanced force acts upon it.”
In addition, it seems that carbon encapsulates kinetic energy, holding potential energy in it. Otherwise, how could it be used for fuel? Carbon contains stored energy from millions of years ago. Thus the molecules which are emitted today as C02 continue to hold energy which causes warming. So if the rate we are pushing these particles out into the environment exceeds our planet’s natural ability to remove or absorb the C02 through forests, oceans etc., there is more energy potential in the atmosphere, increasing the rate of warming.
One way to look at it is to look at the kinetic energy of a car in motion. For example, if I am driving my car, at each speed I travel, I need to leave a certain distance between my car and the car in front of me. (In fact, there is “a quadrupling of stopping distance with a doubling of vehicle speed.” This is because, my stopping distance is reduced proportionately by the rate of speed I am travelling. Thus, if I follow the car too closely at 60 miles per hour, and am required to stop, I may not be able to avoid crashing into the car in front of me.
Our current rate of C02 emissions is causing a similar effect in our environment. In addition, we are not yet able to stop all the various components which are contributing GHG’s, so rather than having one faucet, running water into the sink, we have many. In effect, there is a multiplier effect in the environment that increases the effects of GHGs.
The three simulations showed this, the cause and effect relationship between CO2 emissions and the ability of the natural systems to absorb and reduce the effects, in order to maintain a balance. MIT’s Greenhouse Gas Simulator showed that in order to stabilize CO₂ concentration, we would need to decrease our present levels dramatically. My first estimate in the simulator was to lower CO2 emissions to 4 GTc, to levels at around the 1900s rate, so that the levels do not exceed the net removal rate by nature (i.e. absorption by the ocean or biomass.) This did reduce the levels to a level lower than the stated goal, but that would require a dramatic change for us. For example, if “the annual carbon dioxide emissions increased to about 7.2 GtC (billion metric tons per year of carbon equivalent) in 2000–2005,” this would require a reduction of more than 3 GTc’s based on my model. We’re now in the year 2012. This illustrates that we cannot emit more CO2 than the net removal mechanism can accommodate. (If you’ve ever had a “slow drain” in your house, where when you run the water, the water drains so slowly that the sink fills up, this is similar to how our rate of emissions is exceeding our capacity to remove them. Our atmosphere (sink) is filling up faster than nature (drain) can remove the CO2.)
Next, I attempted to match the historic path of CO₂ concentrations using the proportional, the sink saturation, and the positive feedback scenarios. Each of these scenarios showed the rate of change between the emissions of CO2 and the net removal. In the proportional model, I needed to reduce CO2 emissions by 46% from present in order to meet the goal of 500 ppm by 2,100. In the sink saturation model I needed to cut emissions by 42% and not overshoot. It seemed to produce the closest to reaching the net removal goal. For the positive feedback model, I needed to cut emissions by 54% to meet the goal of around 500 ppm by 2,100. This is because in the positive feedback model, there is a multiplier effect at work where through the warming, a chain effect is set off, such that other factors begin to contribute more CO2, such as soil emission, fires and other factors of positive feedback, while at the same time, the plants and ocean absorb or remove the CO2 at a reduced rate. In the sink saturation model, the limiting factor is that the plants and ocean are becoming more saturated and less able to remove the CO2. The positive feedback scenario has this, plus more sources of C02 emissions. It’s sort of like the filter in my heating system. If it becomes clogged, it can’t do its job.
The next experiment showed the relationship between the economy and CO2 emissions. As people have more spending power, they tend to use more greenhouse dependent tools, i.e. fly, drive more, etc. which adds more C02 to the atmosphere. In this experiment we were able to control the carbon intensity of the economy by using a simulated lever to control the rate of emissions along a historical path. There were three scenarios, no delay, a 20-year delay and a 40-year delay.
In the first scenario, we would need to control the intensity to around .18 to .21 tC/$ to reach a goal of 500 ppm. With a 20-year delay, we would need to reduce this further, to about .04 tC/$ and with a 40-year delay, .01 tC/$. This shows that the longer we delay mitigating or controlling C02 emissions, the more we will need to do later, and, we may not be successful.
Using the Climate Momentum Simulator, there were six different scenarios. This showed that even though emissions are reduced, sea level and temperature continue to rise. This again is due to the momentum, the trajectory, which I explained using Newton’s laws of motion. It’s like a pendulum swinging. Even if you slow things, it takes time to stop the rate of motion already in motion.
These experiments illustrate the IPCC’s results:  “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level….Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”

References:
Attenborough, David. The Truth About Global Warming; – Attributing Climate Change to Humans. YouTube. h
Beall, Allyson, (2012) Lecture Carbon and Climate 2, WSU Media Center.
The Greenhouse Gas Emissions Simulator
Climate Momentum Simulator
The Climate Bathtub Animation