External forcings include natural phenomena such as volcanic eruptions and variations in the sun's output.
Introduction Under conditions of global warming, sea levels are expected to rise for two main reasons: In general, when liquids warm, they tend to expand.
Therefore, if the oceans warm up, their volume should also increase, leading to a rise in the global sea level. If global warming causes glaciers or ice sheets i.
You can test this for yourself by placing a few ice cubes in a glass of water. If the ice cubes are floating i.
For the same reasons, global cooling should similarly lead to falling sea levels. So, if global temperatures have been changing dramatically over the centuries, then we might expect this to have also caused substantial changes in global sea levels.
For this reason, there is a widespread belief that increasing concentrations of CO2 are leading to unusual rises in sea level. In theory, if a large mass of glaciers or ice sheets melted, this could cause a global sea level rise.
Similarly, if glaciers or ice sheets expanded, this could cause a global sea level fall. Photo of Antarctica's Mt. Herschel by Andrew Mandemaker, taken from Wikimedia Commons. Other researchers, such as Dr. James Hansen of NASA GISS, have hypothesised that man-made global warming will be so strong that it could cause the large ice sheets on Greenland, East Antarctica or West Antarctica to suddenly melt, leading to sudden and dramatic sea level rises of several metres, e.
Hansen and others have been promoting these scary scenarios since the early s e. So, are these scary model predictions reliable, and should we be worried?
Well, in this post, we will forget about the models, and look at what the actual data says. We will find that the data suggests that at most sea levels have risen by cm since the end of the 19th century. However, the apparent sea level rise seems to have been relatively constant over the last century.
If it was due to CO2, we would expect to see a dramatic acceleration since the s, as CO2 concentrations increased.
We will also find that there are a number of serious problems with the available sea level data. As a result, much perhaps all of the apparent sea level rise might be due to problems with the data. In other words, we do not actually know if there has been any significant sea level trends over the last century!
Astute readers will object and complain that there must have been some sea level trends over the last century. This is because, from the discussion above, we would expect to see sea level changes, since global temperatures do seem to have changed over the last century whether the temperature trends are man-made or natural in origin.
However, as we will discuss in the next section, this is not necessarily the case. But, for the reasons we will discuss in Section 2it is also theoretically possible that it could have no detectable net effect on global mean sea levels, or even lead to a net fall!
Problems predicting global sea level changes The density problem The density of a liquid tells you the volume that a given mass of that liquid occupies.The global warming pros and cons debate is one of the most fiercely contested in the U.S.
Whilst the global debate is centered around the cons of global warming, there are a small number of potential pros of global warming too.
Global Warming Global Warming is one of the most serious environmental challenges facing the world today. Global Warming increases the earth’s average temperatures of . Causes. This essay on global warming needs to look at the causes of the problem. Global warming is caused by an acute heating of the earth’s atmosphere as .
Essay Global Warming and Its Effects - Global warming is an increase in the earth's temperature due to fossil fuels, industry, and agricultural processes caused by human, natural, and other gas emissions. We're told that global warming is causing sea levels to rise dramatically.
But, this is not shown by the data. In this essay, we look at the actual data.
Global warming is a rise in the surface temperature of the earth that has changed various life forms on the earth. The issues that cause global warming are divided into two categories include “natural” and “human influences” of global warming.
Natural Causes of Global Warming. The climate has continuously changing for centuries.