When I first began studying global warming in 1995 I was extremely optimistic; we knew the science, the cause, the consequences, and the solutions, and it seemed as though a movement to stop the accelerating warming trend was building momentum. Then began a well-roganized campaign of misinformation spread through US media.

Interestingly, at the time I was completely unplugged from main-stream media. I didn’t listen to the radio (only tapes). I didn’t watch television (only movies). I didn’t read newspapers (only peer-reviewed journals and texts). So I was completely out of the misinformation loop.

Instead, I was deeply focused on the science of climate change. I studied paleoclimatology (the long-term history of Earth’s climate). I studied climatology. I studied meteorology. I studied glaciology. And I gained a deep enough understanding of the climate system to earn B.S., M.S., and Ph.D. degrees from 3 separate universities.

When I emerged, I realized that while I was racing ahead in my understanding of climate, the world, or at least a large portion of the US, seemed to be racing backward into a darker age of understanding. This has had several effects on me.

At first I lost my optimism. We were now a decade further along in our loading of greenhouse gasses into the atmosphere, but had made no progress on pursuing policies and implementing practices to slow or stop our emissions. Eventually I became excited — since it seemed as though we’ve already passed some pretty important tipping points, perhaps I’ll bear witness to some fantastic (albeit deadly) changes to the climate system. While disastrous, they will no doubt be fantastic.

Then I began my mission to educate as many as I can on the science of climate change. This is not a political issue any more than Newton’s Laws of Motion or the Laws of Thermodynamics are political.

And the science of global warming is much older than most people realize…

The Science

It is easily demonstrated in a lab that when you pass visible light (sunlight) through a chamber filled with CO₂, the same amount of visible light comes out the other side (CO₂ isinvisible). On the other hand, infrared radiation (heat from the Earth) is absorbed by this gas. So, the more CO₂ you put in your chamber, the less infrared comes out the other side.

The way the Earth maintains its temperature is by emitting the same amount of energy (in the infrared) that it absorbs from the Sun (visible light). Lucky for us, some of the Earth’s heat is trapped by gasses like CO₂, which we call greenhouse gasses (GHGs). Otherwise, the Earth would be too cold for life as we know it.

Unfortunately, however, as we increase the amount of CO₂ (and other GHGs) in the air, more energy from the Earth is trapped and the Earth warms. We see evidence of this in samples of the atmosphere from Earth’s past trapped in ice up to 1,000,000 years old. We can see from detailed climate records that as CO₂ concentrations in the atmosphere have risen and fallen, so have global temperatures.

Now, I would like to point out that global temperatures are not the best way to measure climate change. Climate refers to expected patterns of weather, and patterns are not always reflected by a simple average. For example, we can imagine two cities that both have an average temperature of 75ºF. One city fluctuates on a daily and annual basis between a high of 85ºF and a low of 65ºF (average is 75ºF). The other city fluctuates on a daily and annual basis between a high of 150ºF and a low of 0ºF (average is 75ºF). While both cities share a similar average, their climates are markedly different.

An analogy that I frequently use, too, is the difference between a simmering pot of water (212ºF or 100ºC) and water at a rolling boil (212ºF or 100ºC). Again, the temperature is the same, but the behavior of the fluid is quite different due to a small increase in energy.

A similar phenomenon is seen in our atmosphere. Less energy is leaving the system than is coming in. That excess energy is not all going into a change in temperature, however. Huge portions of that energy are being absorbed by the oceans (with great consequences) and Earth’s ice, which is melting unusually fast.

History of the Science

While others start even earlier and give more details, I will only hit a few highlights.

1824: Jean-Baptiste Fourier first discusses the greenhouse effect (although I think that Al Gore put him up to it)

1861: John Tyndall published that CO₂ and H₂O are greenhouse gasses

1896: Svante Arrhenius proposed that burning fossil fuels will build-up CO₂ and lead to “desirable” warming (it was a cold year)

1938: G.S. Callendar argued that man-made global warming was already underway (was Al Gore born yet?)

1990: The 1980s are declared the warmest decade on record

1995: A general consensus is reached among scientists that man-made warming is underway

2000: The 1990s are declared the warmest decade in over 1,000 years

2003: William Ruddiman publishes that humans have been changing climate for 8,000 years

2007: Man-made warming is declared “unequivocal” by the larger science community

The Signs

I am often asked questions of the sort: “If global warming is underway, why was it so cold this January in Cleveland?”

First, one must realize that weather and climate are two different things. While the average temperature of the Earth is clearly on the rise, it not only fluctuates a bit from year to year, but also the warming is not evenly distributed in space and time. For example, winters and nights tend to be warming fastest (since the Earth cannot cool as readily). The polar regions and mountain regions are also warming especially fast.

But when you warm some places really fast, you tend to cool others. And this gets into more complex climatology, but I will try to explain it simply. Most of our weather patterns are controlled by big waves high up in the atmosphere, often referred to as jet streams. Poleward of these jet streams, the air tends to be much colder than on the tropical side. When a big wave forms in the jet, warm air is pushed towards the poles in one place, while colder air is thrust towards the tropics in the other. In this way, we’ve recently experienced some anomalously cold winters in Florida while Alaskans were getting rained on at Christmas time (is that how you make a baked Alaskan?).

These weather oddities are exactly what is expected. Variability will increase, although more of the extreme events will be on the warmer side than the colder.

In the Middle East, some in Saudi Arabia and Jordan witnessed their first snowfalls last winter.

We are already seeing:

A rise in global mean temperature
A rise in global mean sea level
A drop in Northern hemisphere snow cover
Retreat of 95% of the world’s glaciers outside of Antarctica (more than 2 TRILLION TONS of ice has melted just since 2003!)
Antarctic ice shelves are breaking-up
Antarctic Peninsula is quickly warming
Arctic sea ice melting faster than any predictions
Arctic regions are warming ten times faster than the global average
and much more

What will happen

Global average temperatures will continue to rise by 1–6ºC by 2100
Widespread hunger will strike as many agricultural areas dry out
Severe water shortages will strike, especially the 40% of the population that rely on glacier meltwater
Increases in both air-borne and insect-borne diseases
More extreme weather (e.g. droughts, flooding, heat-waves, and storms)
And the list goes on

Read More

I urge any of those interested to read more on the topic at these sites:
Real Climate’s “Start Here”
How to talk to a Climate Change skeptic
Climate change: A guide for the perplexed
Responses to common Global Warming arguments
Climate Change Debate
Myths about Global Warming
Isn’t the Earth cooling?
Global Warming Myths
Skeptical Science
And finally,
The IPCC’s 4th Assessment Report Summary