|Fig. 1 What comes in must equal what goes out (or else)|
That is scary because, for one thing, another group wrote that a 2 deg. C increase in global mean average temperature was "highly dangerous" (New Study Says Even 2 Degrees of Warming 'Highly Dangerous').
The way this happens is that the planet's heat budget is unbalanced by greenhouse gases being injected into the atmosphere by a civilization that is recklessly using fossil fuels at an increasing rate; a rate that is keeping more and more of the Sun's heat trapped in the Earth's atmosphere and oceans (Fig. 1 oversimplified & not to scale).
|Fig. 2a Ocean temperatures @ 7 depth layers|
|Fig. 2b Average Conservative Temperature|
The graph at Fig. 2a shows past, present, and future temperature changes in the oceans at seven depth layers.
The graph at Fig. 2b shows only the mean average of those temperature changes.
Notice how the same mean average values look quite different when graphed en masse (Fig. 2a) compared to being graphed alone (Fig. 2b).
That is something to keep in mind when viewing the same values being presented in different configurations that make them look different.
|Fig. 3a Absolute Salinity @ 7 depth layers|
|Fig. 3b Mean average Absolute Salinity|
Ocean salinity can be changed in several ways, such as by freshening (fresh melt water from ice sheets, ice shelves, and glaciers entering the ocean), currents, changes in temperature, and upwelling, to name a few.
The way to view the two presentations is to note the high and low shown at the left side of the graph.
For example, the mean average temperature begins at about 5.5 deg. C on both Fig. 2a and Fig. 2b, and stays within the 5.0 - 5.9 degree range as its temperature oscillates up and down by cooling and warming.
Nevertheless, that less than one degree of oscillation looks radical on Fig. 2b while looking quite tame on graph Fig. 2a.
|Fig. 4a Thermal Expansion @ 7 depth layers|
|Fig. 4b Mean average Thermal Expansion|
All of these graphs cover the years 1880 through 2100.
Actual in situ valid data contained in the WOD database (@ datasets CTD and PFL) only exists for the years 1968 - 2016.
So, the pre-1968 and post-2016 values are calculated using GISS temperature records from 1880 through 2016, then projected out to 2100 using the recent peer reviewed paper mentioned earlier (New Study Says Even 2 Degrees of Warming 'Highly Dangerous').
The scientists who produced the paper estimate a bit less that a 5 degree C temperature increase as the high end temperature likely to exist on Earth by the year 2100.
|Fig. 5 GISS temperatures|
The past (pre-1968) is projected in the same manner, combined with PSMSL and WOD in situ measurements as a guide.
You may notice that some of the in situ WOD measurements are more volatile than the other measured values (PSMSL & GISS) during the about half a century of in place measurements we have.
We live in more volatile times now, which makes it difficult to guesstimate both the past (less radical) and the future (more radical), but remember that we are at a 1 deg C GISS anomaly now, and they project it to increase to about a 5 degree anomaly.
That is quite radical too.
The in situ measurements from 1880 - 2016 exist for PSMSL and GISS, meaning the projections are only future computations, but since the WOD measurements are not that robust, pre-1968 and post-2016 must be estimated by being informed by the other measurements.
At the end of the day, it is the trend line that will be the most accurate indicator.