There is a new paper out in the Journal of Climate which some have hailed as proof that the global mean sea level is not influenced by human activity. However, this is exactly the opposite of what the study authors explain are the real results.
The following guest post is a briefing note by the Climate Science Rapid Response Team:
The study finds sea level rise is still continuing at a steady rate. Study author Dr. John Church has stated via email correspondence, “I would argue that there is an unhealthy focus on one single statistic -- an acceleration number -- and insufficient focus on the temporal history of sea level change.”
With a complete reading of the paper, it becomes apparent that acceleration is only one part of the larger picture. The planet is rapidly warming and the seas are rising. These researchers are refining our understanding of which factors are driving that rise, and in what proportions.The study Twentieth-century global-mean sea-level rise: is the whole greater than the sum of the parts? indeed finds that "sea level rise is still continuing at a steady rate".
Confidence in projections of global-mean sea-level rise (GMSLR) depends on an ability to account for GMSLR during the 20th century. There are contributions from ocean thermal expansion, mass loss from glaciers and ice sheets, groundwater extraction and reservoir impoundment. We have made progress towards solving the “enigma” of 20th-century GMSLR—that is, the observed GMSLR has been found to exceed the sum of estimated contributions, especially for the earlier decades. We propose that: thermal expansion simulated by climate models may previously have been underestimated owing to their not including volcanic forcing in their control state; the rate of glacier mass loss was larger than previously estimated, and was not smaller in the first than in the second half of the century; the Greenland ice-sheet could have made a positive contribution throughout the century; groundwater depletion and reservoir impoundment, which are of opposite sign, may have been approximately equal in magnitude. We show that it is possible to reconstruct the timeseries of GMSLR from the quantified contributions, apart from a constant residual term which is small enough to be explained as a long-term contribution from the Antarctic ice-sheet. The reconstructions account for the approximate constancy of the rate of GMSLR during the 20th century, which shows small or no acceleration, despite the increasing anthropogenic forcing. Semi-empirical methods for projecting GMSLR depend on the existence of a relationship between global climate change and the rate of GMSLR, but the implication of our closure of the budget is that such a relationship is weak or absent during the 20th century.Note that last sentence and read the distorted logic and back-pedalling in the comments. One of the "Rapid response Team (RRT)" (equipped with hockey-stick maybe?), Dr. John Abraham ends his comment
In short, saying that the relationship between global climate change and sea level rise is weak is not the same as saying “climate change has nothing to do with sea level rise."Well, no - the abstract says "weak or absent". Apparently "absent" is absent from Dr. Abraham's vocabulary. John Church, co-author of many sea-level papers cited in many reports including IPCC assessment reports and a co-author on this particular paper says
I basically agree with what John Abraham has written.
Sea level is more complex then just a simple linear relationship to surface temperatures. The physics is more complex than this and there are multiple time scales for each of the components contributing to sea level change. Glaciers are a good example. As temperatures continue to rise their contribution cannot continue to rise indefinitely because over time there will be a smaller glacier volume to contribute to sea level riseI see a "straw man" surfacing from the rising waters - who on the CSW page or elsewhere mentioned "a simple linear relationship to surface temperatures"? No -one, though perhaps Abraham would say "it's not the same as saying there aren't any such statements".
Fundamentally, the "rapid-response team" is saying that "Semi-empirical methods for projecting GMSLR depend on the existence of a relationship between global climate change and the rate of GMSLR, but the implication of our closure of the budget is that such a relationship is weak or absent during the 20th century" doesn't mean what it so clearly does say. Even one of the co-authors "basically agree[s] with what John Abraham has written". Is he telling us that the abstract is in error? If so why hasn't it been corrected?
I, as a sceptical observer, would observe that if the correlation between climate change and sea-level rise in the 20th. century is "weak or absent", and that if climate change over that period is hypothesised to be driven by human activities, then the claimed correlation between those activities and sea-level rise is also "weak or absent". But then, I'm not a scientist, and not qualified to comment on a statement in a research paper which one of the authors agrees doesn't say what it clearly does say.
The RRT also says "this is exactly the opposite of what the study authors explain are the real results". How many authors explained "the real results"? Just the one, apparently. Big numbers are clearly not the RRT's strongest suit.
But what about the RRT statement "The planet is rapidly warming" and the comment from co-author John Church "As temperatures continue to rise"? - IPCC AR5 and any temperature dataset refute both of those claims (I'm being tactful using the word). Perhaps they'd both say that a chart which shows stasis or a slight fall in temperature during the 21st century "is not the same as saying there's no global warming" over the same period. "Post-normal science" is all around us, and rising rapidly.