Superfact 147: Global Warming causes sea level rise via Thermal Expansion and the Melting of Land Ice and to a lesser degree from changes in land water storage, such as groundwater pumping and dam construction. However, almost none of the sea level rise is due to the Melting of Sea Ice.
As ocean water warms, it expands, which also raises sea level. Water expands with the temperature as long the temperature is above 4 Celsius. This is referred to as thermal expansion. In recent years, thermal expansion accounts for about 30% to 33% of global sea level rise. The melting of land ice (glaciers, Greenland, Antarctic land ice) accounts for roughly 60% to 66% and 3% to 10% of global sea level rise comes from changes in land water storage, such as groundwater pumping and dam construction. You can read more here and here.
A very small amount, less than 2%, comes from the melting of sea ice (floating Arctic sea ice or ice shelves). Sea ice melt itself does not cause sea levels to rise because the ice is already in the water. When it melts, it displaces the same volume of water it already took up. This is Archimedes principle. It does not add new mass to the ocean. On the other hand, the melting of ice on a land surface, like Greenland, does increase the sea level because new water is flowing into the ocean. It should be noted that the minor contribution of global sea level rise that comes from sea ice stem from the fact that sea ice is mostly fresh water while sea water is saltwater and fresh water and saltwater have different densities. Click here for an explanation.
I consider this a super fact because it is an important fact surrounded by a lot of confusion and surprises. Many people do not know that sea ice contributes almost nothing to sea level rise and would not have contributed any at all if it weren’t for the different salt content of sea ice and sea water. However, the melting of the arctic is a big problem for other reasons.
Other people, often from the climate denier camp, think that they are the only ones who understand Archimedes principle and that sea ice not contributing to sea level rise somehow refutes what climate scientists (or activists) say (it doesn’t of course). Yet others who understand this better still do not know that sea ice does contribute to global sea level rise even though it is very little.
But Global Sea Levels Have Changed Much More in the Past
It may seem like a sea level rise significantly less than a meter cannot be that bad. After all the sea level has changed by much more in the past, even 100’s of meters. However, there are a few things to keep in mind.
First this is happening in an extremely short time. 100 years is a 100 times shorter time interval than 10,000 years. Secondly there are 8 billion people on the planet and hundreds of millions of people are living in areas that are very close to the sea level. Our civilization developed during a period of unusually stable climate and relatively stable sea levels. The CoastalDEM study indicates that up to 630 million people live on land below projected annual flood levels for 2100. In addition, a lot of that land is used for food production. There is also erosion, habitat loss, storms having greater impacts, etc. So, sea level rise is a significant problem.
Global Warming is Chiefly Caused by Burning Fossil Fuels
Another thing to keep in mind is that not only do we know that global warming is happening and that it is happening very fast. We also know that it is caused by us primarily as a result of our burning of fossil fuels. There is a long-standing scientific consensus on these two facts because the evidence is conclusive. We also know that global warming and global sea level rise will continue long after we have halted our carbon emissions.
The sharp spike in the global average temperatures towards the right side of the graph above is caused by us humans, chiefly by our burning of fossil fuels. A very common objection to this claim is “Climate has always changed”, or “I think it is a natural cycle”, etc. Such statements dismiss out of hand the expertise of the scientists who are the experts on past climate and natural causes for climate change. They are nearly unanimously stating that natural causes cannot explain the current rapid global warming, and it is obvious why if you look at the evidence.
To quote Katherine Hayhoe, a well-known climate scientist : “Hi, I’m a climate scientist. You may know me from my greatest hits including, “No, it’s not a natural cycle,” “Yes, I know it’s been warmer before (and the only reason YOU know this is because we scientists told you so)”
Other super facts related to global warming
- Global Warming is Happening and is Caused by us
- The Hockey Stick Graph is not Wrong
- Scientists Agree that Global Warming is happening and that we are the Cause
- Climate change worsens wildfires in the US
- Without carbon dioxide the Earth would freeze
- IPCC Did Not Backtrack on Global Warming Being Human Caused
- Orbital Cycles are not the Cause of the current Global Warming
- The Sun is not the Cause of the current Global Warming
- Volcanoes emit a tiny fraction of carbon compared to humans
- Climate change worsens wildfires Globally and human Land-Use Changes Reduces them
- Carbon Cycle Emissions Does Not Cause Global Warming
- The Most Important Greenhouse Gas Does Not Drive Global Warming
- El Nino or Ocean Currents are not the Cause of Global Warming
- Without the Burning of Fossil Fuels Earth would be cooling
- Natural Causes Cannot Explain the Current Rapid Global Warming
