Last week scientists in Mauna Loa, Hawaii announced that the level of carbon dioxide in the earth’s atmosphere has reached 400 parts per million (ppm). This is a noteworthy and troubling milestone as we consider what sort of a world we will be bequeathing to our children and grandchildren. To “honor” this recent milestone, I have prepared a brief summary of the key scientific aspects of the Greenhouse Effect and implications of crossing the 400 ppm threshold. I’m covering the concepts and trends rather than delving into the numbers and details, which can be found in my earlier columns on this subject.
Below are the top ten things you should know about global warming.
1. To Understand Global Warming you First Must Understand Electromagnetic Radiation
Electromagnetic radiation is a difficult concept to wrap your mind around. Electromagnetic waves are a form of energy which is either absorbed or emitted by particles such as electrons, atoms, or molecules. They travel through space and produce oscillating electric and magnetic fields at frequencies which depend on the energy of the wave. The electromagnetic spectrum is comprised of the full range of possible frequencies for electromagnetic waves. (With me so far?)
To make electromagnetic radiation easier to talk about, we give names to different frequency segments, including radio waves, infrared radiation, light, ultraviolet radiation, microwaves, X-rays, and gamma rays. While the utilization of these names is convenient, it also creates confusion in the general populace who often don’t understand that light, radio wave, and X-rays are basically the same as one another. In order to understand global warming, you need to understand that all of these names refer to electromagnetic waves and that these waves interact with different types of particles in predictable ways.
2. Not Believing in Global Warming is Like Not Believing in Microwave Ovens
When an electromagnetic wave strikes a molecule which has the proper structure to absorb it, energy from the wave is transferred to the molecule. The physics behind this is a bit elaborate, but the essence is as follows. If the energy of the electromagnetic wave is equal to the difference in energy between two orbitals in a molecule that the wave strikes, then the molecule will absorb the wave. Molecules which absorb electromagnetic radiation heat up.
In a microwave oven, electromagnetic radiation with the correct frequency to be absorbed by water molecules is directed at your food causing the water within the food to warm. Once the water is warm, it heats the rest of the food.
The Greenhouse Effect works exactly like a microwave oven. Most of the energy from the Sun which enters our atmosphere has frequencies in the light and ultraviolet portions of the electromagnetic spectrum. Some of this energy, after striking non-reflective areas on the earth, is readmitted into the atmosphere as infrared waves. These infrared rays have the correct frequency to be absorbed by carbon dioxide causing it to heat up. When the carbon dioxide heats up, it heats the rest of the air. The extent of the Greenhouse Effect is proportional to the amount of carbon dioxide in the air. More carbon dioxide means warmer air.
The next time you hear someone say that global warming is a hoax, offer to reheat their coffee in the microwave.
3. Humans Are Adding Carbon Dioxide to the Air, A Lot of It
We know from analyzing air trapped in Arctic ice that in the time period from 400,000 years ago, the time when our species first begamn, until 1850, the beginning of the Industrial Revolution, the carbon dioxide concentration in the atmosphere ranged between 180 and 300 ppm. Since then we have driven the carbon dioxide concentration up to 400 ppm, 33% higher than it has been for the last half of a million years. There is no mystery as to how and why this has happened. When you burn hydrocarbons such as gasoline, coal, natural gas, diesel, or wood, you generate carbon dioxide. Homo sapiens are now living in a set of environmental conditions that our species has never experienced.
4. Carbon Dioxide is Making the Atmosphere Warmer
Since 1850 the global average temperature has increased by 0.9 °C (1.5 °F) in direct correlation with the increase in carbon dioxide concentration. Furthermore, this increase in temperature is speeding up. To bring that point home consider that the twelve years from 2000 to 2012 comprise twelve of the fourteen hottest years since we began keeping temperature records about a century and half ago. (I recommend you pause and read that last sentence again.)
If carbon dioxide concentration where to increase to 450 ppm, the global average temperature is predicted to rise to a level 2 °C above the level from 1850. Two degrees may not sound like much, but consider that during the last ice age, when most of the Northern Hemisphere was covered by massive glaciers, the global average temperature was only 4 °C lower than it is today. A world with 450 ppm of carbon dioxide is going to be far different and far more challenging than what we have experienced as yet, especially now that there are more than seven billion of us.
5. Extraction Fossil Fuels is What Matters
If you start to read a news story about one country or another reducing its carbon dioxide emissions, stop reading and throw it away. Stories about carbon dioxide emissions are nearly always misleading. For example, due to improvements in efficiency and the slowing of the economy, fossil fuel consumption and, thus, carbon dioxide emission in the U.S. are down from a couple of years ago. Sounds good, right? Unfortunately, there is a catch.
Extraction of fossil fuels in the U.S. is way, way up. Coal, oil, and natural gas supplies not consumed domestically are exported to other countries. The key parameter controlling the increase of carbon dioxide concentration in the air is the global rate of fossil fuel extraction. Soon after we bring the coal, natural gas, or oil to the surface, it will enter the atmosphere as carbon dioxide. The atmosphere doesn’t care whether it was burned in Boise or Beijing. At present about 50% of carbon dioxide emission remain in the air with the remainder dissolving in the oceans or being incorporated by plants. Since the world’s oceans are becoming saturated with carbon dioxide, a higher percentage of emissions remain in the air with each passing year.
6. Feedback Loops are Scary
The primary mechanism of global warming since the late 1800s has been the accumulation of carbon dioxide in the atmosphere. As the temperature of the earth increases, several feedback loops have been initiated which are going to accelerate the rate of temperature increase in the future. I review two of these below.
On the ocean floor and within the Arctic permafrost, methane, the primary component of natural gas, combines with water to form a frozen solid known as methane hydrate. The total amount of methane contained in these areas is not precisely known, but we do know that the amount of carbon tied up within them is staggeringly large. When methane hydrates warm up they dissociate into methane gas and water.
The release of methane gas into the atmosphere has a strong influence on the Greenhouse Effect since it is 20 times more efficient than carbon dioxide at absorbing infrared radiation. As the earth has warmed over the last several decades, methane hydrates around the globe have begun to melt. Thawing of methane hydrates will release more methane which will heat the earth which will release more methane, and so on.
The other troubling feedback loop is the dramatic loss of ice cover near to the north and south poles since the 1970. When sunlight strikes a reflective surface like ice, it bounces back off and passes back out through the atmosphere without warming the ground or the air in a significant way. When sunlight strikes non reflective surfaces, like plants, rocks, and water, it heats the surface and then, since it has lost some energy, is re-emitted as infrared radiation. This infrared is then absorbed by carbon dioxide, methane, and other green house gases. Similar to the thawing of methane hydrates, this process is also self reinforcing. Less ice cover makes for a warmer earth which reduces the ice cover and so on.
7. Global Warming Will Reduce our Food Supplies
Global temperature increases will reduce food production in several ways. Plant growth, which is the foundation of our food supply, is driven by the rate of photosynthesis. Photosynthesis requires the action of some delicately folded proteins know as enzymes. When temperatures exceed 85 °F, the structure of the enzymes begins to distort which reduces the rate of photosynthesis until it finally ceases altogether around 105 °F. Therefore, as places like Iowa and Ukraine have more and more hours per year with temperatures above 85 °F, the rate of plant growth and, thus, the rate of food production will drop.
In addition, rapid regional temperature rise can disrupt the functioning of the local ecosystem, often to the determent of plant growth. Plants are adapted to more than just the temperature of their natural range. Other factors include, rain patterns, soil type, daylight patterns, as well as bird and pollinator activity. Therefore, plants cannot simply migrate geographically along with temperature changes. For example, even if the average temperatures in New Jersey rose to what they are currently are in Florida, we cannot expect to be able to grow orange trees in the Camden suburbs.
These two factors will combine to limit our food supply in the coming decades at a time when global population continues to increase.
8. Sea Level Rise Will Have Devastating Impacts
My children and I have a game we like to play at the beach. With the tide coming in, we build a sand castle just beyond the extent of the advancing waves. Then we build a series of sand walls to protect the castle. Soon the tide reaches the defenses and begins to breach them as we work madly to fix our sea walls. It’s fun for a while, and then, inevitably, the walls fail and the castle is washed away. Who knew this little game would be an allegory for the 21st century?
Although estimates for total sea level rise in this century vary greatly, Mother Nature isn’t waiting for us to finish our calculations before getting started. Sea levels are already rising from thermal expansion as the water warms as well as from the melting of polar ice caps. Rising seas reduce the amount of energy required in a storm surge to cause flooding along the coast. Flooding seas cause significant damage to coastal cities and towns and damage farms due to salt infiltration.
As human society developed over the last 15,000 years, we have built the vast majority of our infrastructure, our sand castles so to speak, along the waterfront. The tide is coming, and some of this infrastructure, like the Maldives, the Netherlands, Miami Beach, or Rodanthe, will be overrun.
9. Main Arguments from the Skeptics
It’s not difficult to find people, especially via the internet, who claim that Global Warming is a hoax perpetrated to advance liberal politics. As disconcerting as this can be, it’s not surprising. No matter what the topic, even the Moon Landing, there always seems to be some subset of our population who think it’s a conspiracy. The ranks of the “skeptics” are also filled by people who, in my estimation, aren’t really skeptical, but rather would prefer not to sacrifice their personal comforts and incomes to help ensure that our descendents have a nice place to live. Let me address two of the main arguments advanced by the “skeptics”.
Whenever to variables correlate with one another, one must consider which variable is the cause and which is the effect. In the case of global warming, carbon dioxide and temperature correlate, when one goes up so does the other. I’ve laid out for you the scientific basis for carbon dioxide build-up being the cause and temperature rise being the effect. Some of the skeptics will ask, “How do we know that it’s not the increase in temperature which is driving up carbon dioxide concentration”? It is quite difficult to pull together a coherent argument for this cause-and-effect proposal which can explain the data.
Another common claim from the skeptics is that Global Warming is not real since the number of strong hurricanes striking the U.S. is not increasing. The basis of this criticism stems from poor science reporting from the main stream media. Over the years, many media outlets have stipulated that global warming will bring stronger hurricanes. This is not necessarily true, nor is this the consensus of climate scientists.
We judge the strength of a hurricane based on wind speeds which define the categories storms as one, two, three, four or five. The wind speed of a hurricane is driven primarily by water temperature differences, cold in one place, warm in the other, rather than by absolute water temperature. Therefore if the ocean warm in a relatively uniform way, we would not necessarily see stronger winds generated.
What we do expect from water waters, are storms which will carry higher volumes of rain. Warmer water results in higher rates of evaporation into warmer air which can accommodate higher levels of humidity. Super Storm Sandy of the fall of 2013 is a likely harbinger of other heavy precipitation events to come.
10. There is No Sign as Yet That We Are Taking This Seriously
In order for the concentration of carbon dioxide in the atmosphere to stay below 450 ppm, humanity needs to collectively agree to leave more than half of all known fossil fuel reserves in the ground. This is not going to happen. If North Carolina can’t even agree on higher efficiency standard for new buildings, how can we reasonably expect the Chinese to agree to burn less coal. Sadly, if predictably, the rate at which we are adding carbon dioxide to the atmosphere is growing rather than falling every year and we are ravenously pursuing every possible source of buried hydrocarbons around the world; including the oil sands of Canada and, potentially, methane hydrates buried beneath the sea floor.
As yet, humanity has not made any meaningful efforts to avoid or even to lessen the impact of this coming climate crisis and I don’t believe that we will. In the next twenty years we will be confronted with the full impact of a world 2 °C warmer than 1850 at a time when we will be reaching several other critical resource limitations, particularly supplies of fresh water. In the past, when humanity has been faced with similar resource-limitation challenges, we either migrated away from one another or fought resource-related wars. With no remaining land to which we can migrate, I am sorry to say that I am expecting us to resort to the other traditional option.
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