Summary of Comments from the CCNF Scientist Community:
Dr. Andrew Dessler: This is interesting and will help us shake out problems in our understanding of where heat is being stored in the ocean. That said… this result doesn’t tell us much about how much warming we’ll get over the next 100 years.
Dr. Mauri Pelto: This is a very short term data set, which means it is not robust. The data set also depends on the correct assessment of two other aspects of sea level rise and hence is an indirect measure… [It] is a good approach, but with high uncertainties at present.
NASA Study Finds No Measurable Warming in Deep Ocean Since 2005 [for general commentary]
The world’s deep oceans have not warmed measurably since 2005 according to a new NASA study. The NASA press release announcing the study’s findings was quick to point out that the results do not call into question the theory of man-made climate change, but do “leave unsolved the mystery of why global warming appears to have slowed in recent years”. An excerpt from the press release:
In the 21st century, greenhouse gases have continued to accumulate in the atmosphere, just as they did in the 20th century, but global average surface air temperatures have stopped rising in tandem with the gases. The temperature of the top half of the world’s oceans – above the 1.24-mile mark – is still climbing, but not fast enough to account for the stalled air temperatures.
Many processes on land, air and sea have been invoked to explain what is happening to the “missing” heat.” One of the most prominent ideas is that the bottom half of the ocean is taking up the slack.
Based on the fact that water expands as it gets warmer, NASA scientists at the Jet Propulsion Lab were able to test this hypothesis of “missing” warming hiding in the deep ocean. As explained in the press release, the scientists began with the measure of sea level rise between 2005 and 2013, then deducted the amount of rise due to meltwater (e.g., melting ice sheets and loss of glacier mass worldwide) and then the amount of rise due to the expansion of water from the warming in the upper portion of the world’s oceans (which scientists have good data on). These measurements were based on data from the Argo floats and NASA satellites. Any significant remainder of sea level rise, if their data is correct, would then show that there’s warming in the deep oceans. So what was the remainder? “Essentially zero” according to the scientists.
Perhaps some of the CCNF scientists could share their thoughts on this study?
Dr. Andrew Dessler: This is interesting and will help us shake out problems in our understanding of where heat is being stored in the ocean. That said, the bottom line, that the ocean took up 0.64 ± 0.44 W/m2 of energy over the last decade does not change our estimate of climate sensitivity. So by itself, this result doesn’t tell us much about how much warming we’ll get over the next 100 years.
Dr. Mauri Pelto: This is a very short term data set, which means it is not robust. The data set also depends on the correct assessment of two other aspects of sea level rise and hence is an indirect measure of warming at depth with some critical assumptions. This is a good approach, but with high uncertainties at present.
Previous Forum dialogue on the topic:
Note: A few excerpts were minimally edited for readability; please refer to the links for the exact quotes.
Dr. Scott Denning: The main place that the heat goes in the earth system is in the oceans. Water has a tremendous amount of heat capacity. [See Dr. Denning’s example of jumping into a pool with a temperature of 70 degrees to illustrate this point, starting at 12:94 in the video.] …So when you add heat to the earth, the main place that that heat goes is in the ocean. Give or take about 95% of the warming goes into the ocean. Only about 5% goes into warming the air or the land.
– CCNF Interview with Dr. Scott Denning.
Dr. Andreas Schmittner: The statement that “there has been no significant warming over the most recent fifteen-or-so years” is wrong (or misleading at best) because the ocean heat content shows uninterrupted warming. Because 90% or so of all heat goes into the ocean, this is the place to look for warming. See Global Ocean Heat Content 1955 to present (0-2000m).
– CCNF fact checker post on claim by Dr. Garth Paltridge.
Dr. Judith Curry: The uncertainties in ocean heat content below 700 m are very substantial, see http://judithcurry.com/2014/
– CCNF fact checker post on claim by Dr. Paltridge.
Dr. Andreas Schmittner [responding to Dr. Paltridge’s claim that the observed surface warming could have been caused by internal ocean fluctuations]: Could the Earth’s observed surface warming of the last 50 years have been caused by ocean circulation? Let’s phrase this question as a hypothesis: Changes in ocean circulation have caused the observed surface warming of the past 50 years. We can test this hypothesis because if it were true there must be regions in the subsurface ocean where it has cooled. This follows from energy conservation. Observations, however, show no evidence for cooling of the subsurface ocean. The upper ocean heat content (top 2 km) has clearly increased as several independent estimates show. Here is one estimate [see above graph]:
How about the layers below that? Could the heat come from there? Here is a figure estimating heat content changes for the decade from the 1990′s to the 2000′s showing that the deepest layers of the oceans have also warmed. I’m not aware of observations that show that deep ocean layers have cooled over the last 50 years. Thus, existing evidence does not support the hypothesis. Therefore we have to answer the question with “No”.
Note that the layers below 2.5 km depth have much smaller changes in heat content compared with the surface. This is because the deepest layers are very old and mix very slowly with the surface. Therefore I think that it is extremely unlikely that ocean circulation has caused the surface warming of the last 50 years.
– ‘Deep Ocean Warming’ by Dr. Schmittner
Dr. John Anderson: Tide gauge records are supported by satellite data telling us that the rate of rise has significantly increased within the past two centuries. These combined results indicate that the rate of global sea-level rise averages ~3.0 mm/yr, although the actual rate varies regionally (Rahmstorf et al., 2007; Church et al., 2011; Carlson, 2011). However, within the northwestern Gulf of Mexico, subsidence contributes to relative sea-level rise with rates in east Texas as high as 6.0 mm/yr (Paine, 1993). Regardless of the actual value, this is a multifold increase over the long-term rate of the past few thousand years of ~0.40 to 0.60 mm/yr (Milliken et al., 2008).
The only mechanisms that can cause such a rapid increase in the rate of sea-level rise are heating and expansion of the oceans and melting of glaciers and ice sheets; both are known to be occurring at unprecedented rates for the past few thousand years.
It is well known that prior to this time shrinking ice sheets were the main contributor to sea level rise. In fact, the total rise in sea level that was due mainly to shrinking ice sheets was ~120 meters over the past 17,000 years. Until recently, the contribution of ice sheets to sea-level rise remained unknown and is still debated, but the current acceleration of sea-level rise is attributed to heating of the oceans and melting of land glaciers which is supported by measurements of ocean temperatures and the behavior of mountain glaciers, the vast majority of which are retreating or exhibit signs of instability. With this said, ice sheets are by far the largest potential contributor to sea-level rise. The Antarctic Ice Sheet currently holds the equivalent of 60 meters of sea-level rise in its massive ice sheet, so even minor fluctuations in its mass are important.
The main uncertainty in predicting the actual magnitude of sea-level rise is the contribution from the Greenland and Antarctic ice sheets, but again, both ice sheets are exhibiting signs of instability.
– ‘Global Climate Change Impact on the Upper Texas Coast’ by Dr. Anderson