71

The problem is the increase in the rate of sea level rise. I pulled out some approximate numbers from the figure you presented: Can you see now how the sea level is rising much faster today than a century ago? Sea level rise, as well as climate change are normal things on Earth history. However, most times they happen at a very slow rate, allowing ...


25

Sea level has a strong seasonal signal. The annual variability is less than the daily changes associated with tidal forcing in most locations, but still can be on the order of 5-10 cm (maximum values about 15 cm). The causes of the seasonal fluctuations are mostly associated with seasonal changes in wind intensity and patterns, changes in temperature that ...


20

Earth's radius is about 6400 kilometres. That's 6400000 metres. Let's say that you have a mound 20 metres high, burying an older settlement. Your new "radius" is now 6400020 metres. Let's say that $g = 9.8\ \rm m/s^2$ at 6400, your new gravity will be $g = 9.799939\ \rm m/s^2$. Clearly, this is hardly "lower level of gravity". To make this even less ...


13

The problem is that sea level is increasing faster than ever in last couple thousand years. It is currently rising at 3.2 mm/year according to satellite data: The curve you showed is not a straight line, it is rising at an increasing rate. And the trend is expected to continue: The last IPCC report (2018) on the subject say: Projections vary in the ...


12

Sea level rise from thermal expansion is a very slow process: oceans are 3.7 km deep on average, and water has a very large specific heat capacity. Here's a related diagram from the IPCC Third Assessment Report (page 17): Climate change didn't have much impact on the sea level, yet.


10

I think this XKCD says it all:


9

In addition to other answers... This curve isn't a good comparison to the "natural" state of the Earth, because it starts in 1880. The Industrial Revolution had been in full swing for some time by then, and by that point it had been fuelled by coal for around a century. Every factory was powered by coal, every house was heated by coal or coal gas, and every ...


6

As you say, land and water albedos are very different. Meaning that a square meter of water, in average, absorbs more energy from the sun than a square meter of land. Also water transfers heat vertically more efficiently than land due to convection and it also affects climate by providing a ready moisture source. That said, changes in the surface of land vs ...


5

I just took the sea level elevation rate (mm/yr) graph from Camilo Rada's answer and added: A vertical axis at zero (when the curve is at the point, it means the sea level did not change that year). Red and green colors showing the trend. Hopefully it will speak more to your friend.


5

To address your original concern, no, the fact that there are buildings underground does NOT mean that the surface of the earth is higher than in the past. What is actually happening is that these buildings are subsiding into the ground. How? Believe it or not, earthworms. Worms were once constantly tunneling through the soil underneath ancient buildings, ...


5

As a prescript, your question is firmly within the field of Glacio-Isostatic Adjustment (GIA) modeling of the Earth and the sea level. The main scientific names doing research in this direction are Jerry Mitrovica, W.R. Peltier, Roblyn Kendall, Glenn Milne, Kurt Lambeck, Giorgio Spada, and probably some more that I'm forgetting. It all comes down to, ...


4

As @gerrit commented, a precise calculation would need to incorporate a litospheric model to account for isostatic post-glacial rebound. But the "blurry approximation" you want, can be obtained based only on topographic data. This approximation would be reasonably accurate if the melting of the ice happens quickly. For this, we need topographic data of the ...


3

The whole mass of the Earth, mantle, crust, atmosphere and sea, contributes to the Earth's gravitational field, not just the core. Unless you want to split hairs, the Earth's gravity is the same now as it always was. In case you do want to split hairs, the Earth collects a substantial amount of space dust, meteorites and cosmic debris every year, but no one ...


3

Beside some unnecessary simplifications (like assuming the whole Earth is cover with water) The numbers looks right. IPCC predictions are between 0.3 and 0.8 meters by year 2100 for the most likely scenarios, and I find that perfectly consistent with your numbers. Your calculation yields about 0.98 mm per year from glaciers, which using the actual surface ...


2

The jaguar is a close relative of the Asiatic leopard and must have had a common ancestor within the last 5 million years. The South American tapir is obviously closely related to the Malayan tapir and must also have had a common ancestor within he last 5 million years. While the first statement is more or less correct, the latter is not. The Asian and ...


2

In the Arctic there is mostly floating sea ice and the mass of this does not change the sea level. When snow falls on the floating sea ice the weight of the snow is the same as the weight of the sea water it displaces so there will not be any change in sea level from this. But the snow falling on land during winter is water temporary removed from the sea, ...


2

SLR is thought to be caused by temperature rise, which is caused by CO2 rise and other factors. Temperature has been rising since before 1850. It could be another Question: "Why temperature does not correspond with CO2 levels since 1850". The reconstructions used, in order from oldest to most recent publication are: (dark blue 1000-1991): The ...


1

Assessing sea levels is a complicated business, as there are a number of factors which can affect sea level relative to a fixed point on land. For a start, land levels rise and fall; in some places land is lifted up by plate movements or volcanism, in other places it may fall. Rising and falling atmospheric pressure makes very temporary local changes. The ...


1

Arkaia's answer gives good information on the primary cause, which is the multitude of different astronomical changes that operate on various different timescales. However, there's an additional consideration, which is "storm surge" or, more colloquially, "what the weather is doing". Differences in atmospheric pressure between different areas can lead to ...


1

This article based on 2016 publications shows a global decline during 950 to 1250. Fig. 1 Reconstruction of the global sea-level evolution based on proxy data from different parts of the world. The red line at the end (not included in the paper) illustrates the further global increase since 2000 by 5-6 cm from satellite data. There may be local ...


Only top voted, non community-wiki answers of a minimum length are eligible