Does global warming rate depend on greenhouse gas levels or emission rate?

Context

This question explores the relationship between greenhouse gas emissions, atmospheric greenhouse gas concentration, and the rate of global warming. It investigates whether the rate of temperature increase is directly proportional to the amount of excess greenhouse gases already present in the atmosphere or to the rate at which we are currently emitting these gases. The question also considers the scenario where all industrial emissions are halted, examining whether global warming would cease or continue at a constant rate due to the existing concentration of greenhouse gases.

Simple Answer

• Think of greenhouse gases like a blanket around the Earth; the thicker the blanket, the warmer it gets.
• N is like the thickness of the blanket (amount of greenhouse gases already there).
• dN/dt is how fast you're adding more layers to the blanket (how quickly you're releasing more gases).
• dT/dt is how fast the Earth's temperature is rising (how fast it's getting warmer).
• Global warming rate (dT/dt) is more related to the amount of gases already there (N) rather than just how fast we're adding them (dN/dt); even if you stop adding layers, the thick blanket is still there.

Detailed Answer

The rate of global warming, represented as dT/dt, is more directly proportional to the amount of 'extra' greenhouse gases in the atmosphere (N) rather than the rate at which we release them (dN/dt). This is because greenhouse gases have a cumulative effect. They persist in the atmosphere for extended periods, trapping heat and raising global temperatures. If we stopped all industrial greenhouse gas emissions (dN/dt = 0), global warming would not immediately cease. The existing concentration of greenhouse gases (N) would continue to exert its warming influence. Think of it like a bathtub filling with water. Even if you turn off the faucet (stop emissions), the water already in the tub (existing greenhouse gases) will still be there, exerting its pressure, until it drains out. Similarly, the Earth's temperature would only stabilize or begin to decrease once the concentration of greenhouse gases in the atmosphere gradually diminishes through natural processes, a process that can take many decades or even centuries.

The persistence of greenhouse gases in the atmosphere is a crucial factor in understanding this relationship. Carbon dioxide, for example, can remain in the atmosphere for hundreds of years, while other greenhouse gases like methane have shorter lifespans but significantly higher warming potentials. This means that even if we drastically reduce emissions today, the legacy of past emissions will continue to affect the global climate for a considerable time. The atmosphere is already saturated with greenhouse gases to a degree that is causing significant warming, and the impact of these gases will be felt for generations to come. Addressing climate change requires not only reducing current emissions but also considering strategies for removing existing greenhouse gases from the atmosphere, a concept known as carbon sequestration.

To further illustrate the concept, consider the analogy of a savings account. The amount of 'extra' greenhouse gases in the atmosphere (N) is like the balance in your savings account. The rate at which we release greenhouse gases (dN/dt) is like the amount you deposit into the account each month. The global average temperature (T) is like the interest you earn on the account. Even if you stop making deposits (stop emissions), the balance in your account (existing greenhouse gases) will continue to earn interest (cause warming). The rate at which your account earns interest (rate of global warming) is more directly proportional to the balance in the account (amount of greenhouse gases already there) than to the rate at which you were depositing money.

The question touches upon the complex dynamics of the Earth's climate system. The climate is not a simple linear system, and various feedback mechanisms can amplify or dampen the effects of greenhouse gases. For example, as temperatures rise, ice melts, reducing the Earth's reflectivity (albedo) and causing it to absorb more solar radiation, leading to further warming. Similarly, changes in cloud cover and ocean currents can also influence global temperatures. Therefore, while the amount of greenhouse gases in the atmosphere is a primary driver of global warming, the precise rate of warming can be affected by a multitude of other factors. Scientists use sophisticated climate models to simulate these complex interactions and project future climate scenarios based on different emission pathways.

In conclusion, while both the amount of greenhouse gases already in the atmosphere (N) and the rate at which we emit them (dN/dt) contribute to global warming, the rate of warming (dT/dt) is more directly proportional to the existing concentration of greenhouse gases. Stopping emissions would slow the rate of warming but would not immediately halt it. The inertia of the climate system, due to the long lifespan of greenhouse gases and various feedback mechanisms, means that the Earth will continue to warm until the concentration of these gases is reduced. This underscores the urgency of both reducing emissions drastically and exploring strategies for removing existing greenhouse gases from the atmosphere to mitigate the impacts of climate change effectively. Understanding the relationship between emissions, atmospheric concentrations, and temperature change is critical for informed policy decisions and effective climate action.