There are many problems that arise from energy misuse. That misuse, if allowed to continue unchecked, has the potential to deeply threaten the stability of modern civilization on a global scale and to do harm to our planet and its ecosystems in ways that are pervasive and long-lasting.
Excess Greenhouse Gases
The present rate of use of fossil fuels is releasing excessive amounts of what are known as "greenhouse gases" into the atmosphere. The impact of rising temperatures has become increasingly disruptive to all of the earth's environmental and biological systems - land, atmosphere, oceans, glaciers and polar ice caps, and the biosphere.
Since the Industrial Revolution began in the mid 18th century, there has been an increasing release of greenhouse gases into the atmosphere, largely the result of the burning of fossil fuels. The level of those gases has risen to a level in modern times unprecedented in at least the last 800,000 years of earth history. The result of that accumulation of greenhouse gases is a global warming of the earth, including land, oceans, atmosphere and the polar ice caps.
Rising Sea Level
The level of oceans is rising. Since 1993 the average increase has been approximately 2.6 - 2.9 mm per year. That rate of increase is currently accelerating, likely as a result of global warming, and could cause the oceans to rise by the end of the 21st century, depending on the degree of mitigation implemented to limit release of greenhouse gases, by a conservative estimate of a total rise of at least 52 - 98 centimeters. Other estimates place the total rise at 0.3 - 2.5 meters.
The two main causes of increasing sea levels are (1) expansion due to increasing heat content of the oceans and (2) melting of glaciers and polar ice caps.
The measure of acidity in chemical systems is the pH value. pH values can range from 0 to 14. Values in the range less than 7 are acidic, pH of 7 is neutral, and a pH greater than 7 is basic (alkaline). The oceans are normally slightly alkaline, with a pre-industrial pH value of approximately 8.179. The current pH value of the oceans is approx 8.07, which represents a decline in alkalinity in the last 2-3 centuries.
Increased ocean acidity is caused by increased concentrations of CO2 in the atmosphere, the result of massive combustion of fossil fuels for the generation of energy for modern civilizations. Atmospheric CO2 is absorbed by the oceans and in its reaction with water, releases hydrogen ions that lower ocean pH levels.
As the ocean rises in temperature due to global warming, the upper layers of the ocean become less dense, and the upwelling of nutrients from the denser, lower layers of the ocean declines. Most photosynthesis in the ocean occurs in the upper layers, so the decline in nutrients results in a decline in photosynthesis, resulting in a lowering of oxygen in those upper regions.
In addition, oxygen is less soluble in warmer water than cold, resulting in a lowering of oxygen in the ocean, as the ocean is warmed due to increased global temperature.
Changes in Antarctic Ice
About 98% of Antarctica is covered by the Antarctic ice sheet. It contains about 90% of the ice in the world. If all the ice on Antarctica melted, the result would be a global rise in sea level of about 60 meters (200 feet).
Of particular interest is the West Antarctic Ice Sheet. It is more unstable than the ice in the East Antarctic regions. If the West Antarctic Ice Sheet were to melt enough to start breaking apart and descend into the ocean, it would result in a rise in sea level of several meters.
Decrease in Arctic Sea Ice
Arctic Sea Ice is declining annually at a rate of approximately 9.3% per decade. Although melting of sea ice does not change the level of the oceans directly, it nonetheless does occur because of global atmospheric warming, and that has major implications for the continental ice sheets in Greenland and Antarctica. If those were to melt entirely, it would cause the oceans to rise approximately 60 meters and would result in massive flooding in the world's highly populated coastal areas.