Changes in atmospheric circulation over the past five decades have enhanced the wind-driven inflow of warm ocean water onto the Antarctic continental shelf, where it melts ice shelves from below1, 2, 3
. Atmospheric circulation changes have also caused rapid warming4
over the West Antarctic Ice Sheet, and contributed to declining sea-ice cover in the adjacent Amundsen–Bellingshausen seas5
. It is unknown whether these changes are part of a longer-term trend. Here, we use water-isotope (δ18
O) data from an array of ice-core records to place recent West Antarctic climate changes in the context of the past two millennia. We find that the δ18
O of West Antarctic precipitation has increased significantly in the past 50
years, in parallel with the trend in temperature, and was probably more elevated during the 1990s than at any other time during the past 200 years. However, δ18
O anomalies comparable to those of recent decades occur about 1%
of the time over the past 2,000 years. General circulation model simulations suggest that recent trends in δ18
O and climate in West Antarctica cannot be distinguished from decadal variability that originates in the tropics. We conclude that the uncertain trajectory of tropical climate variability represents a significant source of uncertainty in projections of West Antarctic climate and ice-sheet change.
You are misreading the graph in Figure 2. The (upper) line with the 200-year trend only has the top inset from 1960- as measuring temperature. The longer trend (200 years) below it shows the isotope anomaly, which the authors themselves state is not used as a proxy for temperature.ReplyDelete
"The use of δ 18O in precipitation as a proxy for temperature
is well known, and supported by our data. However, we do not
use δ18O as a proxy for temperature. Rather, we observe that
δ18O in West Antarctica covaries with atmospheric circulation in
a manner similar to temperature."
The same mis-reading applies to the graph you depict above showing a downward slope for the last 2,000 years. Again, that's the δ18O anomaly, not temperature.
This paper probably needs to be removed altogether from this site, as it doesn't support the claims in the summary above.
No, I am not misreading fig 2.Delete
What part of "The use of δ 18O in precipitation as a proxy for temperature is well known, and supported by our data" and "we observe that δ18O in West Antarctica covaries...in a manner similar to temperature" do you not understand?
δ18O is used as a proxy for BOTH precipitation AND temperature in thousands of paleoclimate papers, including this one.
"This paper probably needs to be removed altogether from this site, as it doesn't support the claims in the summary above."
No, I will not be removing this paper from this site nor changing the summary above, which is in fact correct.
The only thing that should be retracted is this fraudulent paper from the scientific literature. For all the reasons why read Steve McIntyre's post:
and read my comment there documenting how fraudster & lead author Eric Steig deleted my inconvenient questions on this paper - twice - at RealClimate:
The authors claim themselves that they "do not use δ18O as a proxy for temperature." That's probably why their *temperature* chart on figure 2 (the upper smaller one) looks a bit different than what's shown on the 200-year trend, which uses *δ18O* for the trend line.ReplyDelete
Also the authors clearly claim (in the abstract) that the last 50 years has seen the largest increase in δ18O in 200 years, which they claim is parallel with the temperature trend, and that 99% percent of the last 2,000 years did not see δ18O as high as what's been observed in the last 50 years.
From the abstract:
"We find that the δ18O of West Antarctic precipitation has increased significantly in the past 50 years, in parallel with the trend in temperature, and was probably more elevated during the 1990s than at any other time during the past 200 years. However, δ18O anomalies comparable to those of recent decades occur about 1% of the time over the past 2,000 years."
How does this latter point support the claims you've made in your summary of the paper above regarding cooling?
This is why I consider this paper to be fraudulent, or at the very least dishonest. They are talking about d18O anomalies ABOVE an arbitrary DECLINING line they drew in fig 2, and they tried to hide that in the text of the paper and deleted my comment about that twice at RealClimate. Please read the link at ClimateAudit I provided. Fig 2 clearly shows d18O is at some of the LOWEST levels of past 2000 years.Delete
I meant to say fig 3, not 2, in the above comment.Delete