@tomnelson2080 2 days ago Wait, potholer: You think that CO2 is the climate control knob, and while CO2 remained stable, Greenland cooled to its lowest point in 10,000 years in 1875, then you want us to believe that humans are the reason for Greenland's warming since then?! Until you can tell us exactly what caused the Minoan/Roman/Medieval warm periods, Dark Ages/LIA cooling, early 20th century warming, & mid-20th century cooling, I refuse to believe you understand natural variability enough to rule it out as the #1 post-1875 warming cause.See this above comment was posted on July 23!! The same lie based on "Figure 4. Temperatures over the past 10,500 years recorded in the GISP2 Greenland ice core. (Modified from Cuffy [sic.] and Clow, 1997)" continues to be claimed on the interwebs and in "real" life. haha. It's based on the below propaganda of "combining" R.B. Alley's graph with Kurt Cuffey's graph. So I emailed Kurt Cuffey to get his response! I will add it to this blog post. thank - see below actual source: Cuffey, K. M., & Clow, G. D. (1997). Temperature, accumulation, and ice sheet elevation in central Greenland through the last deglacial transition. Journal of Geophysical Research: Oceans, 102(C12), 26383–26396.
The GISP2 reconstruction changes the relationship between 18O and temperatures by a factor of two during the Holocene, while more recent reconstructions keep it constant. Similarly, elevation change influences 18O records. The old GISP2 reconstruction did not take elevation changes into account.
10,000 years of temperature history disputes the notion of recent unusual and unprecedented warming.
That vid link displays the error - claiming global warming is debunked. People eat this stuff up!
The first link corrects the error.
https://briankoberlein.com/blog/man-for-all-seasons/
This graph comes from A Reconstruction of Regional and Global Temperature for the Past 11,300 Years (Marcott et al.) a paper published in the journal Science in 2013.2 The graph combines 73 sets of temperature measurements
from all over the world, rather than just one. The blue line is the
best fit of the data, while the pale blue represents the uncertainty
range. You’ll also notice the red spike. That’s our current warming
trend (up until 1990). The paper is particularly interesting because it
looks at the very claim the NIPCC report makes, namely that the Earth
has gone through natural warming and cooling trends for thousands of
years. What Marcott et al. find is that we now have “a global temperature higher than those during 90% of the entire Holocene.”
If you look at the insolation graph above, you’ll see levels will still go down for the next few thousand years, so the natural trend would be global cooling. But global temperatures are actually rising. They are as high as the warmest period of the Holocene, when insolation levels were about 10% higher than they are today.
Another correct of the error -
Human energy expenditure in the Anthropocene, ~22 zetajoules (ZJ),
exceeds that across the prior 11,700 years of the Holocene (~14.6 ZJ),
largely through combustion of fossil fuels. The global warming effect
during the Anthropocene is more than an order of magnitude greater
still. Global human population, their productivity and energy
consumption, and most changes impacting the global environment, are
highly correlated.
https://www.nature.com/articles/s43247-020-00029-y
In total, 60% of all human-produced energy has been consumed since 1950 CE, at 22 ZJ, more than in the entire previous Holocene (~14.6 ZJ: Table 1). Since 1871 CE, the Earth’s oceans have stored ~436 ZJ of solar energy trapped through the increases in anthropogenic greenhouse gases87, and from warming-induced increases in water vapor88, a reinforcing feedback. This is more energy by an order-of-magnitude than associated with direct human production and consumption (at 23.3 ZJ since 1871 CE).
http://glaciers.pdx.edu/fountain/readings/HoloceneClimate/McDermottEtAl2001_HoloceneClimate.pdf
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JC03981
that long-term (500–1000 years) averaged accumulation rate and temperature have been inversely correlated during the most recent 7 millennia of the Holocene; and that the Greenland Ice Sheet probably thickened during the deglacial transition. The inverse correlation of accumulation rate and temperature in the mid and late Holocene suggests that the Greenland Ice Sheet is more prone to volume reduction in a warmed climate than previously thought and demonstrates that accumulation rate is not a reliable proxy for temperature.
Indeed,
the documented large differences between previously ex-
pected and observed calibrations in central Greenland
suggest extreme caution in use of water isotopes in
paleothermometry in the absence of reliable local calib-
rations. The use of atmospheric models (Fawcett et al.,
1997; Krinner et al., 1997; Jouzel et al., 1997) to calibrate
the water-isotopic paleothermometer has great promise.
Beyond that, borehole paleothermometry and gas-iso-
topic thermometry have proved especially valuable in
Greenland.
alternating intervals of isotopically warm (heavy δ18Oice) and cold (light δ18Oice) ice (10).
Ice-core evidence of abrupt climate changes
Richard B. Alley*
The more dramatic of the
warmings have involved '8°C warming (8,
25) and '2x increases in snow accumula-
tion (9), several-fold or larger drops in wind-
blown materials (17), and '50% increase in
methane, indicating large changes in global
wetland area (5, 24).
Temperature converted from ice-isotopic ratios (41) using the glacial-
interglacial calibration of ref. 12, shown in °C.
The previous interpretation of evidence from stable isotopes (d18O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially3 and that a consistent Holocene climate optimum—the unusually warm period from about 9,000 to 6,000 years ago found in many northernlatitude palaeoclimate records4—did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing d18O from GIS ice cores3,5 with d18O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of d18O evidence from ice cores3,6, our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our d18O-based results are corroborated by the air content of ice cores, a proxy for surface elevation7. State-of-the-art ice sheet models are generally found to be underestimating the extent and changes in GIS elevation and area; our findings may help to improve the ability of models to reproduce the GIS response to Holocene climate.
The clear Greenland Holocene climatic optimum now unmasked in d18O records from GIS ice cores brings these records into line with borehole temperature data. This rehabilitates d18O as a reliable temperature proxy, paving the way for temperature reconstructions based on high-resolution d18O records from ice cores.
https://www.nature.com/articles/s41586-022-05517-z.pdf
By systematically redrilling ice cores, we created a high-quality reconstruction of central and north
Greenland temperatures from ad 1000 until 2011. Here we show that the warming in
the recent reconstructed decade exceeds the range of the pre-industrial temperature
variability in the past millennium with virtual certainty (P < 0.001) and is on average
1.5 ± 0.4 degrees Celsius (1 standard error) warmer than the twentieth century. Our
findings suggest that these exceptional temperatures arise from the superposition
of natural variability with a long-term warming trend, apparent since ad 1800. The
disproportionate warming is accompanied by enhanced Greenland meltwater
run-off, implying that anthropogenic influence has also arrived in central and north
Greenland, which might further accelerate the overall Greenland mass loss.
Modern temperatures in central–north
Greenland warmest in past millennium
The most recent 4000 years show a gradual de-
crease in melt events, with the last peak – probably caused
by a single event – occurring around 1000 years before to-
day. The trend in the Middle and Early Holocene appears
to plateau, with some fluctuations. This climatic interpreta-
tion fits well with the generally accepted theory that summer
temperatures decrease throughout the Holocene, e.g., Axford
et al. (2021), and also follows the trend in stable water iso-
topes, a proxy for temperature (Fig. A6a). As melt events
generally occur during summer, our interpretation is consis-
tent with recent results from Bova et al. (2021) indicating
that annual temperatures increase and summer temperatures
decrease throughout the Holocene
https://cp.copernicus.org/articles/18/1011/2022/cp-18-1011-2022.pdf
Quantifying the amplitude of the abrupt warmings recorded in
ice cores is done by calibrating the water isotope palaeothermom-
eter with absolute temperature change estimates derived from
measurements of gas fractionation35–37
.Severinghaus, J. P., Sowers, T., Brook, E. J., Alley, R. B. & Bender, M. L.
Timing of abrupt climate change at the end of the Younger Dryas interval
from thermally fractionated gases in polar ice. Nature 391, 141–146 (1998).
36. Landais, A. et al. A continuous record of temperature evolution over a
sequence of Dansgaard-Oeschger events during Marine Isotopic Stage 4
(76 to 62 kyr BP). Geophys. Res. Lett. 31, L22211 (2004).
37. Huber, C. et al. Isotope calibrated Greenland temperature record over
Marine Isotope Stage 3 and its relation toCH 4. Earth Planet. Sc. Lett. 243,
504–519 (2006)
The ice-core stable isotope records from GRIP, NGRIP, Dye 3, Camp Century, Renland, and GISP2 in Greenland (Johnsen et al., 2001 and references therein) and from Agassiz, Ellesmere Island in Canada (Fisher et al., 1995) have provided continuous, high-resolution proxy records of Holocene temperature variations. These records were corrected for effects from altitude changes due to ice flow and ice-sheet elevation changes (Vinther et al., 2009; Lecavalier et al., 2017). However, the paleo-thermometer deduced from stable water isotopes may be biased because it reflects the temperature only at times of precipitation, it is influenced by temperature changes at the moisture source and changes in the transport path-way, and the relationship between isotope composition and air temperature is complicated by local factors such as temperature inversion strength (e.g., Jouzel et al., 1997). Therefore, other temperature proxies from ice cores have been used along with the isotopic records, specifically melt layers observed in the ice cores which indicate that temperatures had been high enough to produce melt at the snow surface. The quantity of melt layers has been combined with δ18O records to constrain summer temperatures (Alley and Anandakrishnan, 1995; Fisher et al., 1995; Fisher et al., 2011; Herron et al., 1995; Kameda et al., 1995). Snow accumulation is inversely correlated with temperature and can, in similarity with stable isotope ratios, be used as a temperature proxy (Meese et al., 1994). Meese et al. (1994) used a series of annual markers in the GISP2 ice core to construct a snow accumulation record spanning the Holocene period.
Glacier response to the Little Ice Age during the Neoglacial cooling in Greenland
Gravity-driven fractionations of Ar and N2 gas isotopes in the snow column respond to vertical temperature gradients produced by changes in both the temperature at the snow surface and to the accumulation rate. Used in combination, δ40Ar and δ15N from enclosed air bubbles in glacier ice provide a paleo-thermometer that is independent of the conditions for precipitation (Severinghaus et al., 1998) and the GISP2 ice core records of δ40Ar and δ15N have provided a Holocene temperature reconstruction for Greenland (Kobashi et al., 2017). Buizert et al. (2018) reconstructed Holocene temperatures using an inverse modelling of the GISP2 δ15N record. The ice temperatures in glaciers are themselves archives of past temperatures because thermal conductivity is poor in ice. Therefore, Monte Carlo inverted borehole temperature records have been read as accurate, if poorly resolved, temperatures from the past (Dahl-Jensen et al., 1998), and have served as calibrations of the better resolved temperature proxies from ice cores (Fig. 2).
https://www.sciencedirect.com/science/article/pii/S0277379121004819
Buizert et al. (2018) reconstructed summit temperatures by calibrating the GISP2 δ18Oice data by forcing the temperature to reproduce the general trend in δ15N using a dynamical firn-model. Both methods lead to different temperature estimates. In Buizert et al. (2018) an overall uncertainty of 1.5 K was stated for the reconstructed temperature, slightly higher than Kobashi et al. (2017) estimate of 1.21 K. Both approaches have in our view shortcomings: the δ15Nexcess method loses important information about the lock-in-depth (LID) and δ18Oice scaling method does not consider the influence of seasonal distribution of precipitation in particular for faster signals (multi-decadal to centennial). In Döring and Leuenberger (2018), we introduced a new automated method to reconstruct temperature variations using a fitting-algorithm of gas-isotope data based on a Monte Carlo inversion technique coupled to a firn-densification and heat-diffusion model.
https://climatechange.umaine.edu/gisp2/
On 1 July 1993, after five years of drilling, the Greenland Ice Sheet Project Two (GISP2,) penetrated through the ice sheet and 1.55 meters into bedrock recovering an ice core 3053.44 meters in depth, the deepest ice core thus far recovered in the world. With the completion of the GISP2 drilling program and a companion European ice coring effort (the Greenland Ice core Project (GRIP), located 28 Km to the east) a new era in paleoenvironmental investigation has been opened. These records are of extreme significance to our understanding of environmental change because they not only provide the highest resolution, continuous, multi-parameter view produced thus far but as importantly the two records can be used to validate each other(e.g., dating, presence of events, length of the environmental record, presence or lack of discontinuities), the only such experiment of this magnitude in ice core research.
In late 1988 the Office of Polar Programs (OPP, formerly the division of Polar Programs), of the US. National Science Foundation (NSF) officially initiated GISP2.
https://typeset.io/papers/holocene-thinning-of-the-greenland-ice-sheet-33ow4te715
During the Holocene climate optimum 6,000 to 9,000 years ago, for example, many locations in the Northern Hemisphere showed unusual warmth yet changes in Greenland appeared inconsistent. Vinther et al. now standardize the previously disparate-seeming ice core records of climate history on the GIS during the Holocene and find consistent evidence for a stronger climate optimum than was previously recognized, together with elevation reduction and marginal ice sheet thinning.
The previous interpretation of evidence from stable isotopes (δ18O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially3 and that a consistent Holocene climate optimum—the unusually warm period from about 9,000 to 6,000 years ago found in many northern-latitude palaeoclimate records4—did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing δ18O from GIS ice cores3,5 with δ18O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of δ18O evidence from ice cores3,6, our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our δ18O-based results are corroborated by the air content of ice cores, a proxy for surface elevation7. State-of-the-art ice sheet models are generally found to be underestimating the extent and changes in GIS elevation and area; our findings may help to improve the ability of models to reproduce the GIS response to Holocene climate.
Cuffey, K. M., & Clow, G. D. (1997). Temperature, accumulation,
and ice sheet elevation in central Greenland through the last deglacial
transition. Journal of Geophysical Research: Oceans, 102(C12),
26383–26396. doi:10.1029/96jc03981
https://www.sciencedirect.com/science/article/abs/pii/S0277379101001111
glaciers and ice sheets that is isotopically light compared to ocean water (e.g., Dansgaard, 1964; Covey and Haagensen, 1984). A secondary influence on the isotopic balance is that the rate and isotopic composition of precipitation are temperature dependent. Warm climate intervals tend to be associated with an increased precipitation flux and a shift toward isotopically heavier precipitation.
Termed the ‘‘glacial index method’’, its basis is to use the ice core record of d18 O variations, for example the time series from the GRIP site at Summit Greenland (Dansgaard
et al., 1993), in conjunction with modelled changes in surface elevation to construct a temporally and spatially evolving climate forcing encapsulated by the ice sheet surface temperature TSðl; y; tÞ and the ice-equivalent surface mass balance bSðl; y; tÞ:
For example, latitudinal variation in d18 O of surface
precipitation results entirely from the fact that TS (given
by the model climate forcing) varies with latitude
https://www.ces.fau.edu/nasa/module-3/how-is-temperature-measured/isotopes.php
Depending on the climate, the two types of oxygen (16O and 18O) vary in water. Scientists compare the ratio of the heavy (18O) and light (16O) isotopes in ice cores, sediments, or fossils to reconstruct past climates. They compare this ratio to a standard ratio of oxygen isotopes found in ocean water at a depth of 200 to 500 meters.
More evaporation occurs in warmer regions of the ocean, and water containing the lighter 16O isotope evaporates more quickly than water containing the heavier 18O. Water vapor containing the heavier 18O, however, will condense and precipitate more quickly than water vapor containing the lighter 16O. As water evaporates in warmer regions, it is moved with air by convection toward the polar regions.
small adjustments in ice surface elevation that in a constant climate lead to small
changes in surface temperature and surface balance as steady-state conditions are approached.
Cuffey, K. M., Clow, G. D., Alley, R. B., Stuiver, M., Waddington, E. D., & Saltus, R. W. (1995). Large Arctic Temperature Change at the Wisconsin-Holocene Glacial Transition. Science, 270(5235), 455–458.
remaining water vapor that condenses over higher latitudes is subsequently rich in 16O.[3] Precipitation and therefore glacial ice contain water with a low 18O content. Since large amounts of 16O water are being stored as glacial ice,
The coldest sites, in locations such as Antartica and Greenland, have about 5 percent less 18O than ocean water.
Melting returns light oxygen to the water, and reduces the salinity of the oceans worldwide. Higher-than-standard global concentrations of light oxygen in ocean water indicate that global temperatures have warmed, resulting in less global ice cover and less saline waters. Because water vapor containing heavy oxygen condenses and falls as rain before water vapor containing light oxygen, higher-than-standard local concentrations of light oxygen indicate that the watersheds draining into the sea in that region experienced heavy rains, producing more diluted waters. Thus, scientists associate lower levels of heavy oxygen (again, compared to the standard) with fresher water, which on a global scale indicates warmer temperatures and melting, and on a local scale indicates heavier rainfall.
easier to infer temperature from glacier length rather than elevation.
a balance between snow fall (accumulation) and melt.
warming of ocean causes melt, which increases the flow rate also - up to 10 times increase!
However, during the Holocene, where temperature variations are comparatively small, changes in seasonal distribution of precipitation as well as of evaporation conditions at the source region may dominate water-isotope-data variations (Huber et al., 2006; Kindler et al., 2014; Werner et al., 2001).
https://www.sciencedirect.com/science/article/pii/S0277379121004819
To obtain the accumulation rate estimates, three different ice sheet margin retreat scenarios (50 km, 100 km or 200 km scenario) were used as boundary conditions for an ice flow model (see Cuffey and Clow (1997) for details
Comparisons of ice core-based temperature reconstructions during the Holocene with other high latitude proxy records (e.g. sea surface temperature records, North Atlantic circulation proxies, terrestrial temperature records (pollen, speleothems, tree rings)) require a robust temperature record with low uncertainties. Based on the above arguments, we prefer the δ15N-based temperature reconstruction. Our T(δ15N) provides robust centennial to millennial scale variations while decadal variations are more uncertain.
Hi Drew, I'm happy to answer questions, though you should keep in mind that my 26-year-old Greenland work has been superseded by more-recent studies, especially for the Holocene (the last 11,000 years), and in particular by the studies that combine records from a half-dozen ice cores in central and northern Greenland. These studies were lead by the Copenhagen glaciology group, and you can find them on Google Scholar. Bo Vinther was one of the main authors. I read quickly through the "carbonbrief" article to which you linked, and it seems accurate to me. If you read that carefully, it should answer the main questions you have. Having said that, my direct responses RE my study published in 1997 (and its predecessor in 1995): 1. Those studies were primarily designed to examine the glacial to Holocene transition (20--10 kyr ago), and they are *not* the best way to address the issue of recent warming and its millennial context. They captured the start of the current warming but were not designed or capable of resolving it well. And even if they did, it's just for one location in central Greenland. Using one location is a valid approach if examining very long-timescale changes (e.g., the 20--10 kyr transition) but not at all a good idea for decadal-scale changes. The noise at the short timescale requires that you average a group of sites spanning a region. "Noise" means both failures of the proxy record to record climatic temperature accurately, and real climatological / meteorological variability that arises strongly from atmospheric dynamical patterns. 2. In the context of (1), the questions you raise about how accumulation and isotope calibrations are treated in different studies is irrelevant to your concern. Those are minor issues. 3. The entire approach of comparing recent observed warming to past variability *for the purpose of inferring mechanism* is fundamentally a weak argument because the timescale is too short to reconstruct past variability well or, more importantly, to reconstruct the climate forcings well. This argument will become stronger as warming proceeds. 4. Following from (3), the reason we know the recent warming is due to changes of the atmospheric greenhouse is that we can measure the effects on the radiative balance of the planet and compare it to uptake of energy by the planet (primarily manifest as ocean warming) and to other forcings such as solar intensity. Here's an analogy: you are sitting in your house on a cold evening. You pull a thick blanket over yourself and start to feel warmer. Why do you feel warmer? Was it the blanket trapping heat (yes, at least in part, it must be)? Was it your furnace working harder? Was it a sunbeam coming through a window? There are only a limited number of options, and you can know about the role of all of them. In this case, greenhouse gases are the blanket. The sun is your furnace, etc. 5. Following from (4), the evidence is overwhelming that most of the warming of Earth since 1980 has been caused by anthropogenic greenhouse gases and the feedbacks associated with warming. The warming from 1850 to 1950, however, contains a "natural variability" signal in addition to an anthropogenic signal, and this natural component can be regarded as the "end of the Little Ice Age," and it was partly solar and partly volcanic. It is unlikely that we will ever be able to give a confident and fairly precise statement about how much of this earlier warming was anthropogenic vs. natural (most of the warming occurred between 1910 and 1950, as I recall), but there are strong arguments that it was at least half anthropogenic. The problem is we will never be able to head backward in time and launch some satellites to get the measurements needed. Best wishes, Kurt Cuffey ................................................................................................................... Kurt M. Cuffey Professor, Department of Geography, University of California
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