Sea level as a global thermometer

Looking for something else, I stumbled across:

The density of sea water changes with temperature but we have only limited, Argo sampling of the temperature depth and surface temperature metrics. Here local sea level changes provides a mass metric of sea water density. So let's compare to sea surface temperature:


So the area north of Australia shows higher density, suggesting a colder column, that is covered by a thin layer of warmer water. We see some evidence in the waters near the islands north of Australia. Perhaps tidal flows are bringing the colder waters to the surface.

Based upon the El Nino in the eastern Pacific raising sea level and denser water showing up in the western Pacific, I'm wondering if they are linked. In effect El Nino on one side is pushing colder, deep sea waters up on the other side.

Bob Wilson

 

From Jason-2, more recent data:

Source: http://sealevel.jpl.nasa.gov/images/latestdata/ssh/2015/SSHA_20150612_001500.png

Bob Wilson

 

Another interesting data point:

• ~7% change in solar radiance during the year

This might explain the annual sea level change and give another metric for heat changes.

Source: The Earth is Hottest When It Is Furthest From the Sun On Its Orbit, Not When It Is Closest

During the period when the Earth is furthest from the sun (aphelion), the average temperature of the entire planet is about 4°F (2.3°C) higher than when it is closest to the sun (perihelion). On average, the intensity of sunlight falling on Earth during aphelion is about 7% less than during perihelion. Despite this, the Earth ends up being warmer during the period in which it is furthest away from the sun.

So what’s going on here? During the winter months, for the Northern Hemisphere, the overall temperature of the Southern Hemisphere, where it is summer, doesn’t change as much as the other way around. This is because a much larger portion of the Southern Hemisphere, compared to the Northern Hemisphere, is made up of water and water has a significantly greater heat capacity than land. On a similar vein then, during the summer for the Southern Hemisphere, the overall average temperature of the Southern Hemisphere doesn’t increase as much as the Northern Hemisphere does during its summer, for this same reason.

So the “tl;dr” version is: there is a lot more land in the Northern Hemisphere than the Southern Hemisphere; this land heats up much faster than water and water cools down much slower than land. So even though there is less intensity of sunlight during the summer in the Northern Hemisphere, the Earth’s average temperature is higher at this time when it’s furthest from the sun.
. . .

• Summers in the Northern Hemisphere last 2 to 3 days longer than summers in the Southern Hemisphere. The reason why is that the Earth moves more slowly at aphelion than at perihelion.
• The date of the period where the Earth is furthest away from the sun is called Summer Solstice. The date at which the Earth is closest to the sun, is called Winter Solstice. Summer Solstice happens on June 21/22. Winter Solstice happens on December 21/22.
• In between these two points, there is a point in time where the Sun will appear to rise and set along the equator, so that the length of night and day is almost exactly equal everywhere on the planet. These two points are called the vernal equinox (March 20/21) and autumnal equinox (September 22/23).

​

Bob Wilson

 

Recent papers about sea erosion under Greenland and Antarctica glaciers are suggesting mechanisms that might cause some 'step' increases in sea level. So I was interested to find James Hansen and team are seeing a similar risk:

James Hansen, the former NASA scientist whose congressional testimony put global warming on the world’s agenda a quarter-century ago, is now warning that humanity could confront “sea level rise of several meters” before the end of the century unless greenhouse gas emissions are slashed much faster than currently contemplated.

This roughly 10 feet of sea level rise—well beyond previous estimates—would render coastal cities such as New York, London, and Shanghai uninhabitable. “Parts of [our coastal cities] would still be sticking above the water,” Hansen says, “but you couldn’t live there.”

This apocalyptic scenario illustrates why the goal of limiting temperature rise to 2 degrees Celsius is not the safe “guardrail” most politicians and media coverage imply it is, argue Hansen and 16 colleagues in a blockbuster study they are publishing this week in the peer-reviewed journal Atmospheric Physics and Chemistry. On the contrary, a 2 C future would be “highly dangerous.”
. . .
Hansen has long suspected that computer models underestimated how sensitive Earth’s ice sheets were to rising temperatures. Indeed, the IPCC excluded ice sheet melt altogether from its calculations of sea level rise. For their study, Hansen and his colleagues combined ancient paleo-climate data with new satellite readings and an improved model of the climate system to demonstrate that ice sheets can melt at a “non-linear” rate: rather than an incremental melting as Earth’s poles inexorably warm, ice sheets might melt at exponential rates, shedding dangerous amounts of mass in a matter of decades, not millennia. In fact, current observations indicate that some ice sheets already are melting this rapidly.
. . .​

Source: Climate Seer James Hansen Issues His Direst Forecast Yet - The Daily Beast

The paper has not been published, yet, but I look forward to it.

Bob Wilson

 

Huh? I missed that one but already agree. My version would be circular:

Then there is the oral version:

Bob Wilson