Here is what our atmosphere looks like from the Space Station. It is visible as the thin blue line on the horizon. To put it in perspective, the top layer of the atmosphere is less than the distance from New York to Philadelphia, Washington to Richmond, or to Wilmington, Delaware, from London to the South Coast; from -- well you get the point. It's about 100 miles high, and when we launch a Space Shuttle, it takes only 8 minutes from launch to orbit, and only 5 minutes to leave the atmosphere. 85% of the atmosphere is only 25 miles high. The Earth's atmosphere is not very thick, so we don't have much room to maneuver.
Here is a map of the atmosphere. Please click on it. The atmosphere of the Earth may be divided into several distinct layers. We need to understand these layers to understand what is happening in them. So from the ground up.....
The troposphere is where all weather takes place; it is the region of rising and falling packets of air. The air pressure at the top of the troposphere is only 10% of that at sea level (0.1 atmospheres). There is a thin buffer zone between the troposphere and the next layer called the tropopause.
Above the troposphere is the stratosphere, where air flow is mostly horizontal. The thin layer in the upper stratosphere has a high concentration of ozone, a particularly reactive form of oxygen (hence the name). This layer is primarily responsible for absorbing the ultraviolet radiation from the Sun. The formation of this layer is a delicate matter, since only when oxygen is produced in the atmosphere can an ozone layer form and prevent an intense flux of ultraviolet radiation from reaching the surface, where it is quite hazardous to the evolution of life. There is considerable recent concern that manmade flourocarbon compounds may be depleting the ozone layer, with dire future consequences for life on the Earth. We have taken a fair amount of action to reduce fluorocarbon emissions, thus proving that we can make changes if we try! However, these chemicals are still in use in household appliances, such as Refrigerators and Air Conditioners and in Car Air Conditioners.
The Mesosphere and Ionosphere
Above the stratosphere is the mesosphere and above that is the ionosphere (or thermosphere), where many atoms are ionized (have gained or lost electrons so they have a net electrical charge). The ionosphere is very thin, but it is where aurora take place, which means that this layer is responsible for absorbing the most energetic photons from the Sun, and for reflecting radio waves, thereby making long-distance radio communication possible -- and protecting us some more from solar radiation (which causes skin cancers).
The structure of the ionosphere is strongly influenced by the charged particle wind from the Sun (solar wind), which is in turn governed by the level of Solar activity.
OK, so now you know what protects and enables life on Earth. Now, what's happening? First, it's important to remember that we live on a planet, and it is one of those planets that is constantly in flux. Tidal changes, volcanic eruptions, earthquakes, and human developments are in the mix. For our part, we are a growing population, and we lose forests for food (animal grazing and crops), for example. We are also increasingly industrialized so that we burn carbon through cars, factories and house warming and cooling. Combining the natural events, and our own needs appears to have resulted in some changes to the composition of our fragile atmosphere. We quickly need to determine the severity of our actions, and develop economically viable solutions, if need be.
In my role as a NASA Solar System Ambassador, we are provided with frequent training sessions from some of NASA's top scientists and engineers, including those working on climate change issues.
Recently, we have had several sessions where we were told by scientists what they think they know, and new questions that are lingering.
How is the Global Earth System Changing?
Earth is currently in a period of warming. Over the last century, Earth's average temperature rose about 1.1°F (0.6°C).
In the last two decades, the rate of our world's warming accelerated and scientists predict that the globe will continue to warm over the course of the 21st century.
Once again the clock below details the changes:
Is this warming trend a reason for concern? After all, our world has witnessed extreme warm periods before, such as during the time of the dinosaurs. Earth has also seen numerous ice ages on roughly 11,000-year cycles for at least the last million years. So, change is perhaps the only constant in Earth's 4.5-billion-year history.
Climate Scientists note that there are two new and different twists to today's changing climate:
(1) The globe is warming at a faster rate than it ever has before; and
(2) Humans are the main reason Earth is warming. Why? Since the industrial revolution, which began in the mid-1800s, humans have attained the magnitude of a geological force in terms of our ability to change Earth's environment and impact its climate system.
How? Since 1900, human population doubled and then doubled again. Today, more than 6.5 billion people inhabit our world. By burning increasing amounts of coal and oil, we drove up carbon dioxide levels in the atmosphere by 30 percent. Carbon dioxide is a "greenhouse gas" that traps warmth near the surface. We anticipate that the global population will be 9 billion by the middle of the 21st century.
Humans are affecting Earth's climate system in other ways.
For example, so far, we have transformed roughly 40 percent of Earth's habitable land surface to make way for our crop fields, cities, roads, driveways, livestock pastures, etc. We also released particulate pollution (called "aerosols") into the atmosphere.
Changing the surface and introducing aerosols into the atmosphere can both increase and reduce cloud cover. Thus, in addition to driving up average global temperature, humans are also influencing rainfall and drought patterns around the world.
While scientists have solid evidence of such human influence, more data and research are needed to better understand and quantify our impact on our world's climate system.
So, what is the scientific world doing about all this? Primarily and quickly, we need to understand what exactly is going on. We have been, and are, launching a slew of spacecraft, One of these was the Orbiting Carbon Observatory was supposed to measure the carbon emissions and reflective radiation. The OCO, failed to reach orbit early 2009. There are still other data sources including spacecraft, high-altitude balloons, ocean sensors and more, world leaders will have better data to make decisions. The OCO will turn out to be a big loss though. You can read about NASA Earth Science missions on this great site.
One thing -- you have to stop calling all this, "Global Warming". That is a definite misnomer. It is "Climate Change". Currently, it looks like some areas will warm while others will cool. In a way, that is only a sideshow. The real issue will be providing water and food to the mass of humanity.
Other than the fashionable notion of "the Carbon Footprint", there are serious observed and predicted effects of changes in water vapor that are these:
The good news of the above is that there will be faster sea lanes from Europe and N. America to Asia and vice-versa. The bad news is that countries are already jockeying for payment for rights of passage.
This fundamentally boils down (pun intended) to this:
Together with the Carbon emissions, we see this:
So, it might be a good time to think about farming in Saskatchewan or Argentina. Why?
(when the lecturer says California, that was only an example. As I said before, this is true of glaciers in many low-latitude regions).
We honestly don't know the accuracy of these scenarios, hence the accelerated research globally. But here is the executive summary recently provided to the US President and Congress:
This all being said, still a number of prominent people dispute these trends. So, who and what to believe?
My own view is that, with an atmosphere as thin as ours, a growing population, and some worrying data about water shortages -- and as someone who grew up in the aftermath of World War -- we need to quickly check our data, and if needed, take personal, political and economic action. My understanding is that there is not much we can do about the Carbon Dioxide already in the atmosphere. It's likely to stay there for at least five centuries. What we consider the tropical latitudes (Cancer and Capricorn) will likely expand. The trick will be to slow our rate of increasing this problem and to grasp opportunities for new businesses, new ways of doing business (for example, working at home), and helping the people seriously impacted by the change.
So what can you do? Simply put, click on the next image:
There are plenty of sites that will help you:
The Nature Conservancy
The United States Government -- Environmental Protection Agency
For a further definition of what exactly is a carbon footprint, go here.
It's very easy for people to dismiss the potential, by looking out of their windows and seeing no great change.
Here are some images from glacial melt:
In a way, it doesn't matter what the causes of climate change are, we are seeing some serious changes, and we need to adapt.
Finally, here is a short video, from Sally Ride PhD, (the first American woman to fly in space) on her thoughts about the climate.
This article from Wikipedia is a great analysis of what we know and see right now.