The Earth is warming. There is no doubt about it. We are spewing carbon dioxide, a “greenhouse gas” into the atmosphere at an alarming rate: it comes from human respiration, from power plants, from automobiles, from livestock, from forest fires, and from a myriad of other sources. In fact, we’ve finally exceeded the figure of 0.04% of the atmosphere being carbon dioxide. This may not sound like much, but it’s actually a lot. In the Middle Ages, the amount was only about 0.028%; we’ve increased that now by over 140%. And we’re still accelerating our rate of carbon dioxide emissions.
Carbon dioxide is not the only greenhouse gas. Water vapor (H2O) and methane (CH4) are both more potent greenhouse gases than CO2. In fact, methane is about thirty-four times more potent than carbon dioxide. However, this is as measured in the long term - a century. If measured over a two-decade period, the figure is actually eighty-six times more potent. This is because methane does not stay in the atmosphere as long as carbon dioxide. This is measured by half-life, and it’s on a curve, so the less methane in the atmosphere, the more slowly it drops out. Fortunately, the amount of methane in the atmosphere is only 1.8 parts per million, but this is still an increase of about 50% over the last two centuries. It’s estimated that as much as 20% of current warming is due to methane. There are many sources of methane, including fossil fuel extraction and livestock gasing, but the critically dangerous source is from methane clathrates in the frozen tundra and in the Arctic seafloor. As the Earth, and disproportionately the polar areas, warm, these clathrates are being released as methane gas into the atmosphere, and at an accelerating rate.
Water vapor is actually the most potent greenhouse gas of all. Its concentration in the atmosphere, rather than in clouds, can be over 4%. However, it’s usually less than 1%. Fortunately, water vapor has a relatively short half-life in the atmosphere. But we are loading the atmosphere with large quantities of water vapor, largely from contrails and power plants. The proportional contribution of water vapor to global warming may be as much as half of the warming.
The deniers will say that we’re not seeing the warming that was predicted, but that is a red herring. We have learned that the atmosphere is not warming as fast as expected simply because the oceans are absorbing more of the heat than expected. The heating is still there, but it’s going in some slightly different pathways.
The planet is not warming evenly. In fact, there are areas that are expected to be cooler. However, the overall trend is warming. The polar areas are warming much faster than the rest of the Earth, and the oceans are warming faster than land masses.
The greatest fear overall appears to have been, so far, melting of the continental glaciers on Antarctica and Greenland. Complete melting of these could raise sea level globally by as much as 70 meters (over 220 feet). There is strong geological evidence that historic melting periods have resulted in a 20-meter (66-foot) rise over a 500-year period.
However, justifiably a greater fear should be attached to the melting of methane clathrates in the Arctic tundra and in the Arctic seafloor. There are billions of tons of methane so far segregated in these deposits, but they are starting to be gased out into the atmosphere with rising temperatures. The emissions of methane are threatening runaway global warming that cannot be coped with by humans.