The Science Behind Greenhouse Gases

Posted on May 24, 2012 by bradleydibble

“All science is either physics or stamp collecting.”
- Ernest Rutherford, Nobel Prize-winning physicist (1871-1937)

I’m always amazed that so many climate change skeptics and deniers have a hard time believing the concept that as we add our emissions to the atmosphere every year, we can’t be at least part of the cause for the global warming and climate change we’ve been observing over the last half-century. We’re adding greenhouse gases such as carbon dioxide, methane and nitrous oxide, and although methane is twenty times more potent a greenhouse gas than carbon dioxide, it’s the sheer volume of carbon dioxide that makes it the bigger problem.

I’m a firm believer that if people properly undertand the science, then they’ll understand why so many of the world’s scientists are concerned about this issue, and perhaps even become concerned themselves. I find the physics behind greenhouse gases fascinating. What is it about these particular molecules that give them their property of trapping heat in our atmosphere?

First, let’s quickly review which gases make up the bulk of our atmosphere:

Nitrogen (N2) - 78%
Oxygen (O2) - 21%
Argon - 0.9%
Carbon Dioxide (CO2) - 0.04%
Methane (CH4) - 0.0002%
Water vapour (H2O) - variable, on average 0.4% throughout the atmosphere

Notice that nearly 100 percent of the atmosphere is made up of gases that aren’t greenhouse gases. Neither nitrogen nor oxygen contribute to the greenhouse effect.

The main greenhouse gases in our atmosphere are: water vapour (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (NO2), and ozone (O3). All of these are trace gases in much smaller amounts than nitrogen or oxygen.

Although water vapour is the largest component, and also a more potent greenhouse gas than carbon dioxide, it’s generally a fixed amount. We can’t add more water vapour to the atmosphere because the excess will simply precipitate out. (Unless, of course, global warming continues; warmer air can hold onto more water vapour than colder air—one of the reasons we experience more extreme weather phenomena such as hurricanes as part of climate change). And don’t misunderstand me, we need these gases, just not in excessive amounts. It’s estimated that without them our planet’s average temperature would be about 33 degrees Celsius (59 degrees Fahrenheit) colder than it is now.

Even if you know nothing about physics or chemistry, you might notice something different about the greenhouse gases compared with oxygen and nitrogen. For one thing, they all have more than two atoms, and all of them other than ozone have combinations of different types of atoms. These larger molecules have a property that nitrogen and oxygen don’t share: they can absorb infrared radiation, also known as heat energy. They function as insulators in our atmsophere, helping to trap all of the radiating heat from our planet’s surface, reflecting it back rather than letting it escape into space.

It’s the same thing as a greenhouse which helps plants grow in a warmer environment than the outside temperature would normally allow. Visible light gets in, some of it is reflected back—green plants look green because that component of visible light is reflected back to your eyes—but most of it is absorbed. Much of the absorbed energy from light is converted into infrared radiation and that’s the heat you feel in a greenhouse.

Our atmosphere functions the same way. Visible light from the sun gets through the atmosphere and some is reflected back (blue from oceans, green from forests, yellow from deserts), but much is aborbed and then reflected back as infrared radiation. Just like the glass in a greenhouse, greenhouse gases allow visible light through, but trap heat in the infrared.

How these gases do that is a bit complicated, but a simple way to think about it is they start to vibrate more when exposed to infrared radiation. If you think of the bonds that hold atoms together inside a molecule as springs, then as greenhouse gas molecules get exposed to infrared radiation, they abosrb that energy and the springs start to vibrate more quickly, squeezing together and pulling apart more vigourously, even bending the bonds if they absorb enough energy.

Since all of these greenhouse gas molecules are surrounded by nitrogen and oxygen molecules, it’s not hard for them to transfer some of that energy to the non-greenhouse gases which in turn start to vibrate more energetically themselves. In that way, the whole atmosphere ultimately becomes warmer thanks to the physical properties of the trace amounts of these few molecules in our atmosphere which contain more than two atoms.

Since our human activities contribute so much added greenhouse gases—30 billion tons of carbon dioxide added each year alone—it’s not surprising that we’re playing a part in climate change. Most climate scientists think we’re playing the biggest part. But even if deniers and skeptics want to hold onto the belief that climate change is part of a natural cycle, wouldn’t it make sense that we should avoid aggravating it even further and do our best to curtail our emissions by looking to renewable sources of energy?

It all comes down to simple physics.

Paleoclimatology: Today’s Science Explaining Yesterday’s Climate

Posted on April 6, 2012 by bradleydibble

“The truth will set you free, but first it will piss you off.” —Gloria Steinem

I recently made a blog post online as well as wrote a letter to the editor in response to the March 19th Maclean’s cover story about Canada having a warmer and drier winter than it has in 65 years. It ended up getting more responses than I usually elicit. Some people expressed doubt about the whole concept of global warming and how the changes we’re seeing now are unprecedented. Because our planet has gone through various ice ages with interglacial periods between them, many question whether what we’re seeing now is any different. Should we really blame our greenhouse gas emissions?

In my book, I explain how subtle changes in Earth’s orbit help to explain many of those past changes. Properties of our planet’s annual trip around the sun changes its axis with time via changes in its tilt or obliquity, eccentricity and precession. All of these contribute to changes our planet goes through over many thousands of years in something referred to as Milankovitch cycles. (You can see a nice visual demonstration of these properties here.) These cycles don’t play a part in the recent concerns about global warming, however, because the changes we’re currently experiencing are taking mere decades, not the millennia necessary for subtle changes in orbit to occur.

Changes in solar energy output—known as irradiance—can contribute to changes in shorter time intervals than the Milankovitch cycles, but that won’t explain the recent findings of global warming either. That’s because the last sunspot cycle was much lower than average. Referred to as a deep solar minimum, it was the lowest energy output our star has provided in nearly 100 years. Our global temperatures plateaued over the last decade because of this minimum: rising greenhouse gas emissions were offset by a decrease in average solar output. Our current sunspot cycle is also a bit lower than usual, but if we had an average or even robust sunspot cycle, we’d be in even more trouble than we are now.

Some people doubt the data. When I posted comments about some of these facts, I had a few responders question where the data were to support what the carbon dioxide levels were in years past. Roger Revelle and Charles Keeling started measuring these levels in 1958 in Hawaii and Antarctica, but what about older records? Some skeptics doubted we’d have anything more than a thousand years old.

So I had to educate them about the Antarctic ice cores. It’s been known for decades that by drilling deep into the ice in Antarctica, we can retrieve little pockets of air within the ice containing samples of our atmosphere as it was when the ice was formed. SInce Antarctic ice doesn’t melt from season to season, it slowly accumulates with time, preserving little samples of air indefinitely.

So how far back can we look? Well, the Dome C ice core drilled down more than three kilometres, and it turns out the oldest samples of atmosphere are 740,000 years old. As a result, we now have measurements of greenhouse gas levels spanning eight glacial cycles. This allows us to know exactly how high carbon dioxide levels were in years past. It’s interesting to see that in nearly 800,000 years of Earth’s atmospheric history, it never experienced levels higher than 300 parts per million (ppm). That is, not until after our human activities started to add to the mix. Combustion of fossil fuels, deforestation and agriculture for 7 billion people add 30 billion tons of carbon dioxide into the atmosphere each year, with most of it lingering there for centuries. The climb in levels started after the Industrial Revolution and the steepness of that climb hasn’t faltered.

We’re currently at carbon dioxide levels in our atmosphere of 392 ppm, a level not seen in nearly a million years, and very possibly much longer, perhaps as much as 20 million years. That level is climbing about 2 ppm each year, and with no end in sight to this rate of rise. Thanks to the Dome C ice core, “the grand-daddy of ice cores” as it’s sometimes called, we have the facts.

Skeptics can think what they want, but we’re the cause of these unprecedented changes to our atmosphere and we’re already seeing the consequences with climate change. Ancient ice ages due to Milankovitch cycles aren’t our fault; little ice ages due to decreases in solar output aren’t our fault. But melting ice caps and glaciers, and increases in extreme weather such as floods and droughts due to climbing greenhouse gas emissions? We have no one to blame for that but ourselves.

Living Green: Small Changes Bring Big Benefits

Posted on February 1, 2012 by bradleydibble

Patients often ask me, “How can I lose weight so I can be healthier?” If I had the universal answer that worked for everyone, I’d be a very rich man. But there are a number of suggestions that help. Most of these are well-known: increase physical activity, cut out excess calories, eat healthier foods, and the list goes on. But one point I emphasize consistently is that Rome wasn’t built in a day, and weight loss isn’t going to happen overnight. People have to take baby steps in their approach, and make small changes at a time. If enthusiasm leads to a dramatic overhaul of an entire lifestyle, I can pretty much guarantee that the changes won’t stick. But if small adjustments are made one at a time, people have a much better chance at sticking to them long-term.

What does any of this have to do with living green? Well, experience has shown that if people make dramatic changes, even if the zeal and enthusiasm is there to support them, human nature being what it is, these changes typically slip back into the old patterns of behaviour with no success achieved. But if people make small adjustments, a little at a time, each little benefit adds up and the overall result can be substantial, and much easier to stick to permanently.

Here’s a list of eight simple things that you can do around the house – small changes that will lead to a greener lifestyle. No one change is too onerous, and if each one is taken one at a time over the coming months, it will be much easier to stick with them. Since some of them have a little extra cost to them, it also makes it easier on the pocketbook if the changes are made gradually. And you can be proud knowing that what you’re doing is healthy for the environment, because your carbon footprint will be substantially reduced.

Install low-flow shower heads. These reduce the amount of water you use during a shower, and since that water is heated, you save on how much energy you use to heat that water.
Replace all light bulbs with compact fluorescent bulbs when they burn out. The days of incandescent bulbs are over. Every standard light bulb in your house should eventually be a CFB. They cost more up front, but use much less energy and last much longer, so in the long run, they’re a good value. And your electricity bill will drop.
Use a programmable thermostat. When people are sleeping, and when people are away during the day at school or work, it makes little sense to heat the home to its normally comfortable temperature. But it’s also impractical to be adjusting the thermostat up and down twice a day. It’s much easier to program a thermostat to do all of the adjustments for you. You can save a lot of energy heating your home by keeping the temp lower when no one is around to need it.
Walk and bike more instead of always driving. Most people who live in urban settings can do a lot more getting around by their own energy rather than starting up the car. And since exercise is so beneficial to heart-health, it has double benefit. Perhaps your regular activity routine can incorporate trips to the grocery store, walks with the dog or visits to a friend’s house. It’s amazing how often we decide to hop in the car because we think our lives are too busy to afford the extra minutes it would take to get their on our own power.
Eat one less meal of meat a week. Consider having Meatless Mondays become a part of your weekly schedule. Since cattle generate their own emissions of methane, the less beef we eat the less emissions. In North America, we tend to eat more meat than we need to anyway. So this green choice is also another heart-healthy one: less meat, more fruits, vegetables and fiber are the recipe. And of course, make sure you’re buying local, from farmers’ markets and local produce in your grocery store. That way there’s less fuel used to get those goods to you.
Eliminate bottled water. It’s expensive and creates a lot of waste to recycle or, more typically, simply get thrown out. If you buy a filter for your water at home, you can have all the clean drinking water you want without needing to have all that plastic as part of it. And when you go to work or the gym, simply take your own water in a reusable container rather than buy a bottle.
Hold onto electronic items longer. Just because the latest smart phone has come out doesn’t mean you need to replace the one you have, frequently less than a year old anyway! Newer may be exciting, but it’s a lot of unnecessary waste if we always want to have the latest gadget available. Wait until a replacement is truly needed and make sure you properly dispose of your e-waste when you finally do replace the old one.
Have a home energy audit. For a few hundred dollars, you can learn exactly where you’re wasting energy, and such simple measures as caulking windows and sealing doors can more than pay for itself. There are often government rebates available if you make changes based on the audit as well.

Try to make a few of these simple home adjustments in the coming year. Each little step makes a difference, and when added together, you will make a significant impact on your carbon footprint!

Politics Aside: The Climate Crisis

Posted on December 14, 2011 by bradleydibble

Before I put politics aside—as the title of this blog suggests—I want to make one important distinction. I want you to appreciate the difference between a political philosophy and a political ideology. With a political philosophy, you have a group of views and theories that help guide behaviours and actions. A political philosophy will allow itself to be open to new evidence, and a new approach when experience dictates that “business as usual” isn’t working. Also, compromise is a viable option. With a political ideology, however, there is a greater chance to hold onto those principles to an unbending degree, with less likelihood to waver from those views and theories, even when common sense, evidence, or experience suggest a different approach is better. Compromise is not so much an option. I think the world would be a better place if we all tried to hold more to political philosophies rather than political ideologies.

I can’t think of any issue where putting politics aside is more important than the environment. We don’t have to cast aside our philosophies, but we could certainly do without our ideologies. The former US Senator Daniel Patrick Moynihan put it best when he said “You are entitled to your own opinion, but not your own facts.” With the climate crisis, there are so many sound bites that occur throughout the various media sources on a daily basis that it’s difficult to know what’s truth and what’s not. When it comes to knowing what course of action we need to take for something like global warming, we have to look to the facts rather than hold onto the ideologies that wail us.

The five facts I list below are undisputed and without contention. Anyone who denies these facts is simply misunderstanding the science, or choosing to ignore it. The facts are as follows:

Carbon dioxide and methane are greenhouse gases. The size and configuration of these molecules, each containing different atoms within them—which sets them apart from oxygen and nitrogen—have a natural ability to absorb infrared radiation energy and, thus, increase in temperature when exposed to infrared radiation. These molecules don’t absorb energy from visible light so their temperature doesn’t increase from the sun’s light until it hits the Earth’s surface and bounces back in the form of infrared radiation. Nitrogen and oxygen molecules which make up 99 percent of our atmosphere don’t absorb energy so much from infrared radiation. But they do absorb energy from the nearby greenhouse gases with which they come in contact. The more of these greenhouse gas molecules there are in the atmosphere, the warmer our planet will become simply because of these scientific properties.
Burning fossil fuels (coal, oil and natural gas), burning down forests, and agriculture all add greenhouse gases to the atmosphere.
Greenhouse gas levels have been rising consistently for the last 200 years or so, but were stable in the atmosphere for thousand of years prior. As we dump nearly many millions of metric tonnes of them per year into the atmosphere, this increase should be no surprise. Since the Industrial Revolution, we’ve increased the amount of the atmosphere’s greenhouse gas concentrations by nearly 40 percent, from about 280 parts per million (ppm) to the present level of about 390 ppm, simply by doing the activities listed above in fact number 2.
Global temperatures are increasing. Recorded temperatures since the 19th century and evidence looking back into our planet’s history even earlier have shown a sharp and unwavering increase in global temperatures that would be predicted from the greenhouse gases our activities have been adding. Other factors that affect global temperature such as changes in the sun’s energy output don’t explain this observation.
Climate change is already happening as a result of increasing global temperatures. The increase in violent storms in both summer and winter, the increase in coastal flooding, the melting of ice at the North and South Poles as well as many of the planet’s glaciers are all, sadly, predicted when facts 1-4 are taken into consideration.

If we are to avoid extremely serious and dire consequences for our planet in the next few decades, and especially for our children and grandchildren, then we have to heed these facts, put aside our political ideologies, and make the changes that will save our planet from ourselves, and for our future.

Comprehending the Climate Crisis

Posted on November 14, 2011 by bradleydibble

Why would a cardiologist write a book on global warming? Well, first and foremost, my concerns about climate change stem more from being a concerned citizen of this planet. However, as physicians we have a duty to care for people in our communities, and not just those who are sick; we also do our best to prevent health problems. I believe that duty extends beyond those who step into our offices. Additionally, cardiovascular and respiratory patients are particularly sensitive to changes in temperature and humidity, so many of the types of patients I treat are going to be the most susceptible to adverse effects on health due to climate change. Lastly, I’ve gained a lot of experience throughout my career in taking complex concepts in health and disease and explaining them to the public in ways that are easy to comprehend without missing the crucial elements necessary for proper understanding. I felt it was important to take those skills and apply them to my efforts in educating people about the climate crisis.