More than a few people in my meager sphere of coworkers, family, and acquaintances are of a decidedly conservative bent and apparently bathe in the fetid wellspring of the Fox network for their daily ablutions. I recognize this because more than a few use substantially the same phraseology as they express the similar contentions on politics or of some duplicitous liberal miscreant. Most are admitted non-sciency folk and have heard that the current dust-up about AGW, Anthropogenic Global Warming, derives from assertions of a self-serving conspiracy by unscrupulous scientists angling for grants or in service of some deeper, darker purpose.
Like many people I’m trying to follow and comprehend the topic of climate change and AGW. Having taken no more than an undergraduate semester of meteorology and oceanography as well as flight training, I can grasp basic concepts and use some of the vocabulary in a sentence. So, when I’m asked for my opinion I usually just shrug my shoulders and offer a scenario for consideration.
Forget CO2 for a minute. What happens to surface water if the atmosphere and oceans get a bit warmer? It’s safe to say that, generally, there will be more moisture entering the air. It’s a fact that water vapor is a greenhouse gas. Water vapor absorbs infrared energy from the sun. Any influence that manages to cause the atmosphere to hold more water is an influence that will cause the atmosphere to capture more thermal energy and result in warming. Being more buoyant that dry air, moist air can convect to produce clouds.
The change from liquid water to gas is an endothermic process. Energy is absorbed to produce water vapor from surface water. During cloud formation, upwelling air naturally cools and condenses to aerosols and droplets. These may freeze to ice and liberate the latent heat of fusion. This is an exothermic process, liberating latent heat which warms the air causing further convection. So, a parcel of moist air convecting upwards will result in an inrushing of surface air which is drawn upwards to sustain a column of rising moist air. The early cloud building phase of a thunderstorm (cumulonimbus) is characterized by strong updrafts from convection.
So, one might expect storm behavior to change as the relative humidity increases. As the average air temperature rises, the higher latitudes (north and south) might be expected to see some change as well.
In the northern hemisphere one of those changes could be the melting of higher latitude snowpack and glacial ice. Ice and snow pack consists of fresh water. Fresh water is less dense than salty ocean water. As fresh surface water runs onto briny oceanic water, it will tend to stratify according to density with lower density, less briny water tending towards the surface.
The thermohaline circulation, also referred to the Atlantic conveyor, is responsible for the gulf stream current that flows in a northeasterly direction along the Atlantic coast of North America and into the north Atlantic. This current is responsible for delivery of relatively warm water to the north Atlantic. These warm waters are partially responsible for the temperate climate of the UK and northern Europe. One of the most important concepts of climate science is that one cannot separate the oceans from climate. Due to the considerable heat capacity and latent heats of water (relative to air), the oceans are a substantial reservoir of energy capacity in direct thermal contact with the atmosphere.
The gulf stream’s arrival to the cooler north Atlantic where the water increases its salinity and density due to low temperature and evaporation to form a region of sinking water that forms a subsurface current. This current circulates to the Pacific and Indian oceans and eventually back to the north Atlantic in a loop of circulating water. For the north Atlantic, this loop is at the surface and transfers heat back to the north Atlantic in the form of warm surface gulf current water.
The gulf stream submerges between the coast of Norway and Greenland. In doing so, warm water is transferred to the north Atlantic. Should Greenland undergo a sudden warming with subsequent release of melted fresh water, it would be expected that the process of sinking of briny surface water would be suppressed due to the presence of less dense surface melt water from Greenland. The effect would be to suppress the potential energy of descending cold briny water feeding the Atlantic conveyor as well as oxygen transport to the ocean depths. Upwelling water from the deep transports vital minerals to support the food chain. The loss of this upwelling will have a distinct affect on the fisheries.
If it transpires that the loss of heat transport to the north Atlantic results in a general cooling of that body of water to form ice, how is the overall heat balance of the earth affected? Could it trigger another ice age?
The point of this is to offer that a rise in air temperature can lead to consequences that are not intuitively obvious. Talking about global warming should not end with just “warming”. The ramp up to global warming is a disturbance that may have surprising results.