Sunday, June 28, 2015

Paper finds 'pronounced influence of solar activity on global climatic processes'

A paper published in Palaeogeography, Palaeoclimatology, Palaeoecology finds "a pronounced influence of solar activity on global climatic processes" including in "Asia, Europe, North and South America, Australia, and the Arctic and Antarctica."


The authors find evidence from spectral and wavelet analysis of influence of the de Vries (∼ 200-year) solar cycle on climate variation in Central Asia, and that,
"Analysis has shown that climate response to the long-term global solar forcing has a regional character. An appreciable delay in the climate response to the solar signal can occur (up to 150 years). In addition, the sign of the climate response can differ from the solar signal sign. The climate response to long-term solar activity variations (from 10s to 1000s years) manifests itself in different climatic parameters, such as temperature, precipitation and atmospheric and oceanic circulation. The climate response to the de Vries cycle has been found to occur not only during the last millennia but also in earlier epochs, up to hundreds of millions years ago."
Tree-ring temperature reconstructions from the paper show 5 more non-hockey-sticks.
Wavelet analysis shows "pronounced" climate variability correlating to the ~200-year de Vries solar cycle (as well as other periodicities)
Prior posts related to the de Vries solar cycle influence on climate

Long-term climatic changes related to solar forcing were examined using millennium-scale palaeoclimatic reconstructions from the Central Asian mountain region, i.e. summer temperature records for the Tien Shan mountains and precipitation records for the Tibetan Plateau. The reconstructions were based on juniper tree-ring width records, i.e. Juniperus turkestanica for the Tien Shan and Sabina przewalskii for the Tibetan Plateau. The data were processed using spectral and wavelet analysis and filtered in the frequency range related to major solar activity periodicities. The results obtained for various tree-ring chronologies indicate palaeoclimatic oscillations in the range of the de Vries (∼ 210-year) solar cycles through the last millennium.
The quasi-200-year variations revealed in the palaeoclimatic reconstructions correlate well (R2 = 0.58–0.94) with solar activity variations (Δ14C variations). The quasi-200-year climatic variations have also been detected in climate-linked processes in Asia, Europe, North and South America, Australia, and the Arctic and Antarctica. The results obtained point to a pronounced influence of solar activity on global climatic processes.
Analysis has shown that climate response to the long-term global solar forcing has a regional character. An appreciable delay in the climate response to the solar signal can occur (up to 150 years). In addition, the sign of the climate response can differ from the solar signal sign. The climate response to long-term solar activity variations (from 10s to 1000s years) manifests itself in different climatic parameters, such as temperature, precipitation and atmospheric and oceanic circulation. The climate response to the de Vries cycle has been found to occur not only during the last millennia but also in earlier epochs, up to hundreds of millions years ago.

Wednesday, June 24, 2015

New paper shows N. Greenland was warmer during early 20th century (1920-1940) & during Medieval Warm Period

A new paper published in Climate of the Past Discussions reconstructs temperatures from 12 ice cores in Northern Greenland over the past 1100 years and demonstrates temperatures during the Medieval Warm Period beginning ~1065 years ago were warmer than at the end of the record in 2000. In addition, the data shows temperatures ~1450 AD (during the Little Ice Age) and from 1920-1940 were also considerably warmer than the latter 20th century, the opposite of expectations of anthropogenic warming theory:

d18O ice core temperature proxy shows Medieval Warm Period in red box labeled "MCA", Little Ice Age in blue box labelled "LIA" and Early Twentieth Century Warming (from 1920-1940) in red box labeled "ETCW". Temperatures of the early 20 century from 1920-1940 were considerably warmer than the latter 20th century, opposite the expectations of anthropogenic warming theory. 
In addition, the paper shows a reconstruction of August Arctic sea ice extent over the past 1000 years (purple line in middle graph below) demonstrating that sea ice at the end of the record in the late 20th century was near the average of the past millenium and about the same as during the Medieval Warm Period:

Spatial and temporal oxygen isotope variability in northern Greenland – implications for a new climate record over the past millennium
S. Weißbach1, A. Wegner1, T. Opel2, H. Oerter1, B. M. Vinther3, and S. Kipfstuhl1
1Alfred Wegener Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
2Alfred Wegener Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Potsdam, Germany
3Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Denmark

Abstract. We present for the first time all 12 δ18O records obtained from ice cores drilled in the framework of the North Greenland Traverse (NGT) between 1993 and 1995 in northern Greenland between 74 to 80° N, 36 to 49° W and 2000 to 3200 m a.s.l. The cores cover an area of 680 km × 317 km, ~200 000 km2 or 10 % of the area of Greenland. Depending on core length (100–175 m) and accumulation rate (90–200 kg m−2 a−1) the records reflect an isotope-temperature history over the last 500–1100 years. 

The δ18O signal in northern Greenland is influenced by temperature, accumulation and the topography of the North Greenland ice sheet between 72 and 80° N. About 12 % of the variability can be attributed to the position of the single drill sites in relation to the ice sheet topography. 

Lowest δ18O mean values occur north of summit and east of the main divide. In general, ice cores drilled on the main ice divide show different results than those drilled east of the main ice divide that might be influenced by secondary regional moisture sources. 

A stack of all 12 NGT records and the NGRIP record is presented with improved signal-to-noise ratio. This stack represents the mean δ18O signal for northern Greenland that is interpreted as proxy for temperature. Our northern Greenland δ18O stack indicates isotopically enriched periods compared to their average during medieval times, about 1420 ± 20 AD and from 1870 AD onwards. The period between 1420 AD and 1850 AD was isotopically depleted compared to the average for the entire millennium and represents the Little Ice Age. The 20th century has isotopic values higher than the 1000 years mean and is comparable to the medieval period but lower than about 1420 AD.

Prof Emeritus of Chemical Engineering explains why 'it is impossible that significant climate change is solely due to increased CO2'

Dutch Professor Emeritus of Chemical Engineering and thermodynamics, Dr. Dick Thoenes, explains a multitude of reasons that, 
"My conclusion is that it is impossible that significant climate change is due solely to an increase in CO2 levels. This means that all measures to reduce CO2 emissions are pointless. This has enormous financial consequences for the world."
Google translation from the German EIKE website:


My views on the influence of CO2 on the climate

The Dutch professor em. of Chemical Engineering at the Eindhoven University and author of many reference books on mass and energy flows in materials, exactly the areas that need the climate science, Dick Thoenes, pushes for anyone interested in clear and understandable why the postulated greenhouse effect in the real world is not seen.


1. Why we believed that more CO2 would warm the atmosphere?

This idea was based on the results of laboratory tests of Svante Arrhenius, which had been published in two studies in 1896 and 1906. He concluded from his first measurements that infrared rays are absorbed by air containing CO2, which heat is released.The surface of the earth receives energy from the sun, where it is converted into infrared radiation, which is at least partially absorbed by the atmospheric CO2, creating a temperature rise occurs. The temperature at the earth's surface also increases in order to ensure a constant flow of heat into the atmosphere.This is called "greenhouse effect". From the heated air layer, energy is transported upwards.

 

2. How important is the greenhouse effect of CO2?

Arrhenius was interested in this effect, because he wanted to explain the warming of the atmosphere after each ice age. Meanwhile it became clear that we owe the relatively mild temperatures of the atmosphere combined the greenhouse effect of CO2 and water vapor (which is however questioned by some scientists). The effect of water vapor is by far the biggest. Arrhenius supposed that the atmosphere in the future would be warmer because of the burning of fossil fuels. This is called the "additional greenhouse effect". He estimated that this effect would account for a doubling of CO2 concentration is about 5 ° C; the former concentration was about 300 ppm. In his second trial he corrected this value to only 1.6 ° C. In the eighties of the last century has often referred to this first study, and it was feared that the rising CO2 content would result due to the increasing burning of fossil fuels to a significant warming of the atmosphere.The second study was, I believe, was not discovered until after 2000. The effect appears in less threatening, but still significant. So far as I know, this second estimate is now considered to be correct.
(Note: It is sometimes claimed that the earth's surface is heated by the heated air back reflection layer containing CO2 but this is wrong, because heat can not flow from colder to warmer temperatures.)

3. Has the "additional greenhouse effect" of CO2 been proved in the real world?

No it has not! It is impossible to conduct appropriate experiments in the atmosphere. In the atmosphere was observed no significant warming in the 20th century, in spite of a huge increase in the CO2 content. There was only one heating 1979-1998 by 0.4 ° C. From 1940 to 1979, gave a slight cooling by 0.2 ° C, and by 1998, the temperature had remained constant. The mean increase in 1940 was about 0.2 ° C. The CO2 content has increased throughout this period. If the measurements do not match the theory, the theory is wrong. [Media {especially the Süddeutsche Zeitung} and see the policy course the other way around. Hold the theory of right and wrong measurements. Note. D. Trans.]
Also, we should carefully deal with the term "air". Originally, the term referred to the local climate of a country or a region. If we now read in the newspapers of "the climate", it is meant an average "global climate". However, such a climate does not exist and can not be clearly defined. Likewise, a "medium temperature" can not be uniquely determined (see section 6).

4. Why do not we notice an additional greenhouse effect?

The greenhouse effect of CO2 has not yet confirmed neither in laboratory experiments on real observations. Although the hypothesis of Arrhenius quite plausible, so it lacks  any scientific  evidence. The reason may be that he is too weak to make itself felt and is therefore superimposed by stronger forcings.
The physical constellation in the atmosphere is much more complicated and can not be reproduced in the laboratory. In the real atmosphere, several additional phenomena occur simultaneously, as there would be solar radiation, reflection on water and ice surfaces, evaporation, convection (vertical ventilation), cloud formation (which radiate upwards and solar radiation reflected), rain, snow, etc. We can simultaneous occurrence and the interactions between these phenomena can not predict, especially because they vary significantly from one area to the next. It is important to note that the evaporation and cloud formation any counteract warming and act as a negative feedback. In fact, has not been shown conclusively that a CO2 increase in the atmosphere has a definite influence on the climate.

5. Are there any other factors that affect the climate?

Yes, there are two natural phenomena that can affect the temperature and fluctuate unpredictably. These are the solar activity and the major ocean currents. The solar activity (which is manifested by sunspots) gives the "solar wind", ie a flow of charged particles emitted by the sun and fly into space. They also hit the Earth and interact with cosmic rays (which comes from distant stars). This in turn affects the formation of clouds in the atmosphere, which determines how much solar radiation reaches the earth's surface. Through this complicated mechanism ensures higher solar activity for higher temperatures in the atmosphere. The solar activity is slowly changing and unpredictable. During the last quarter of the 20th century, solar activity was high, decreased after 2000 and is currently (2015) is very low. It is possible (but not proven) that the measured increase in temperature of 0.4 ° ​​C from 1979 to 1998 is due to the high solar activity.
The great ocean currents distribute the excess heat that is produced in the tropics, over the entire surface. When flows in a given year a little more warm water to one of the poles, it is a bit warmer there. And vice versa. This also affects the average global temperature. So far as I know, the reason for these changes in the ocean currents is still completely unknown. Both of these effects may be the reasons for the variations in the average temperatures of the world, which may vary from one year to the next between 0.1 ° C and 0.5 ° C.

6. Complications and uncertainties

There are significant uncertainties, not only in terms of the quantitative effects of CO2, but also in terms of the mass balance of the CO2 fluxes. These mass balances are quite complicated. The different natural sources, which are much larger than the human emissions are not known with sufficient accuracy. The four sources rivers are: The emergence of CO2 through decomposition of plant parts, the release of CO2 from warm seawater, the absorption of CO2 from the air by growing vegetation and absorption (solution) of CO2 in cold seawater. These sources are each about ten times larger than the human emissions, and are subject to change gradually over time. However, these changes can not be measured accurately. Therefore we can not say with certainty whether a CO2 increase is due to the burning of fossil fuels in the atmosphere, although it seems plausible (but doubtful, see below). An increase can also be searched in a temporary increase in the natural formation or a decrease in the natural reduction (which are not directly linked).
Another hit and miss affair, the proportion of human CO2 emissions remaining in the atmosphere. Of all that enter the atmosphere CO2 fluxes, both natural and anthropogenic origin, around 98% are absorbed by nature (plants and oceans).The remaining 2% in the atmosphere corresponding to the measured increase in the CO2 content. It is not clear whether this has any relation to human CO2 emissions.
What makes the magnitude of these shares determined? Will they remain constant? That's not safe. As a result of increasing the CO2 content of the atmosphere increases plant growth around the world gradually. Therefore, the CO2 absorption will increase by plants, but ultimately also the decomposition of dead plant parts. We can not accurately assess these developments. It may be so, that the 2% (which accumulate) gradually increase or decrease. In the latter case, the CO2 content can be constant (that is of course speculation).
(It is sometimes claimed that about half of human emissions remains in the atmosphere, but this is certainly wrong. The natural absorption processes do not distinguish between CO2 from various sources. The error is based on the observation that the accumulation of CO2 is approximately equal to the half of human emissions, but that's just a coincidence).
The oceans contain about 50 times more CO2 than the atmosphere, mostly as bicarbonates. When the temperature of the ocean rises a little, more CO2 is released into the atmosphere, and when it cools down, goes back more CO2 in the water. Small changes in the CO2 content of water correspond to large changes in the atmosphere. Moreover, some of the CO2 will be permanently removed from the cycle by the formation of calcium carbonate (CaCO3) as shells of marine organisms that sink to the bottom. We do not know how much the mind, but possibly the proportion is not negligible.The limestone cliffs z. B. at Dover in England and many other places around the world are created.
A further complication is the fact that the solar radiation reaching the earth's surface is simultaneously transported upwards through three processes: evaporation, followed by condensation, and cloud formation, heat transfer by convection and infrared radiation followed by (partial) absorption. Although the emphasis is usually on radiation, this is actually the least important (10 to 20% of the whole). This limits the greenhouse effect. Energy is transported through these three processes upwards, but ultimately the power of the upper layers of the atmosphere is radiated into space.A quantitative description of these processes is hardly possible, since they vary considerably between one point and the next.
We know that the evaporation of surface water (including water from wet earth) plays an important role in our climate.When the temperature starts to rise, and the evaporation, which slows down the heating increases (therefore, temperature variations in humid countries like the Netherlands is smaller than in dry areas such as deserts). Also evaporation leads to cloud formation, which hinder the radiation to the Earth's surface. These processes reduce the greenhouse effect (so-called negative feedback). We can not accurately measure this on a global scale.
Another uncertainty is the greenhouse effect of water vapor, which is much larger than the CO2 effect and varies enormously over the world. We can not accurately assess this effect. Therefore it is not possible, a given change in temperature alone the CO2 assign [doing this is exactly what make IPCC and company, without exception! Note. D. Trans.]
A significant uncertainty is the fact that it's not really possible to define an average temperature of the atmosphere. We can amounts of mass or energy resources, but "quantities" of temperature, there is not, so we can not convey. The reported average temperatures are calculated from temperature measurements from around the world in a special way and be extended to the areas from which no measurements exist. This calculated mean temperature is not constant, it can vary without any external influence. This can happen in the form of the sequence of phase transitions as evaporation, condensation, ice melt, ice, evaporation over ice and ice formation in moist air. All these processes are coupled with production or consumption of heat. The extent of these phase transitions can vary in the wake of variations of water or air currents. And they cause warming or cooling of the environment. All these phenomena take place against the background that the atmosphere and the oceans are not in balance.
For example, if observed that in certain periods ice sheets have melted (as it periodically happens), this is not a sign of the warming of the globe ', but rather of its cooling. When ice melts, the environment is (usually water) removed from heat.
This situation of imbalance caused by the fact that the earth is constantly supplied heat or removed from this (because of the solar radiation and the infrared radiation into space). This leads to a large extent on water and air currents around the Earth. One consequence of this is that it is not possible to calculate an average temperature with an accuracy better than 0.5 ° C (see the end of section 5). Small deviations of the mean temperature are therefore not significant. The fact that an average "Climate Change" can not be defined addition follows.

7. The unpredictability of the climate

For a long time it was assumed that the future climate can be predicted if we had knowledge of the following two things:
● A climate model, which describes the Earth's climate in sufficient detail (in this case, is a model, a set of mathematical equations).
● Adequate climate data (from all over the world) that can be included in the model, to put it in a position to predict the future climate.
However, both are wrong. There are too many uncertainties (section 6) in order to form a sufficiently accurate model.Our current climate models are very progressive, but do not represent all of the relevant processes. But even if we had such a perfect model, we could not predict the future climate, as the world's climate as a "chaotic" system behaves.Chaos is in this sense a mathematical concept which means that the system is described by a number of simultaneous non-linear differential equations. Such systems are extremely sensitive to their initial conditions, such as temperatures, which are measured at certain points at certain times. Small variations of these data (less than the measurement accuracy) can lead to completely different results. Therefore, the future of the global climate can not be predicted.

8. warms the world or not?

This question can not be answered. We can ask the following questions that can be answered: Has the world warmed so far? You expect a warming of the world in the future?
Measurements show that has warmed the atmosphere in the period from 1979 to 1998 0.4 ° C, but it is doubtful whether this is significant (see section 6). Even before 1940 there was a slight warming, but there was then no CO2 emissions, so that there must be other reasons.
We can not say whether or not the world is warming in the future, because the climate is essentially unpredictable (Section 7). However, we can expect have. We know that, have been already absorbed about 90% and converted to heat by the infrared radiation that can be absorbed by CO2. If the CO2 content rises, the absorption can of course never rise above 100%. This will lead to a warming below 2 ° C. However, we also know that it would have more advantages than disadvantages. The advantages are: higher yields and lower energy consumption (which would be reflected savings per year in billions of dollars). Because of the negative feedback of the temperature rise is likely to be much lower (unfortunately). Many astronomers say in the near future require a cooling, which would be significantly detrimental than a warming.

9. We can draw a conclusion?

We had originally thought that there would be a relationship between the CO2 content of the atmosphere and the average temperature. This was demonstrated for the geological history, during the last few hundred thousand years.However, showing the geological research, that a temperature increase of an increase of the CO2 content always preceded was (no doubt by gas emissions from the oceans). There is no evidence that CO2 can cause significant warming (more than a few tenths of a degree). We now know that the large number of running processes in the atmosphere is so complex that we can never produce a quantitative description.
Should not we be worried about the fact that we continue to blow large amounts of CO2 into the atmosphere? As far as we know, has a higher CO2 content only benefits (better plant growth), but no disadvantages. In certain geological periods, the CO2 content was much higher than today without any dramatic effect.
(Some people push a possible acidification of the oceans to the CO2 in the shoes, but I believe that is unlikely. The ocean water is slightly basic, and a little more CO2 can be a little less basic, but never acidic).

10. Consequences

My conclusion is that it is impossible is that significant climate change is due solely to an increase in CO2 levels. This means that all measures to reduce CO2 emissions are pointless. This has enormous financial consequences for the world.

About the Author:

Prof. Dr. Dick Thoenes b.1930 taught chemical engineering until 1995, the year he Emiretierung, at the Eindhoven University, Netherlands. He is the author of many books and worked as a research consultant for many companies and the Swedish and Netherlands Governments. He was chairman and is now an honorary member of the KNCV (Royal Chemical Society) and became the Foreign Member of the Royal Academy of Engineering Sciences (IVA) Stockholm appointed. 
He focuses on "Transport phenomena" (the first in the famous book by RB Bird, et al., 1960 formulated). This includes fluid flow, mixing, mass transfer, heat transfer, evaporation, radiation, etc. These phenomena are the basis of chemical engineering and they are also the basis for climate research. So when the second assessment report of the IPCC was published in 1995 (the year of his retirement), he studied it and thought: That can not be true! Later studies confirmed this impression.

Wednesday, June 3, 2015

New paper finds another non-hockey-stick in central Asia

A paper published today in Quaternary Science Reviews reconstructs temperatures in central Asia over the 1074 years from 931 A.D. to 2005, and which shows another non-hockey-stick with temperatures during the Medieval Warm Period around 1000 AD of 18C, the same as reconstructed temperatures of 18C at the end of the record in 2005. 

Comparison of temperature observations to reconstructed temperatures since 1940 is shown in the first graph below, and shows observed temperatures in 1940 (~17.2C) were the same as at the end of the observational record in 2010. 

Although the authors claim "recent warming exceeds any other time in the reconstruction," the observational data shows that the warming peak from 2000-2005 resolved by the end of the record in 2010 to the same temperatures observed in 1940. Further, the warming peak 2000-2005 is within the error estimates (shown in grey below in graph b) during the Medieval Warm Period ~1000 years ago, and the rate of warming from ~950 to 1050 faster than during the 20th century. 




We reconstruct temperature in Mongolia from 931 to 2005 C.E.
Recent warming exceeds any other time in the reconstruction.
We find general agreement with the Medieval Climate Anomaly and Little Ice Age trends.
We observe evidence of significant volcanic influence on Mongolia.

Abstract

Warming over Mongolia and Central Asia has been unusually rapid over the past few decades, particularly in the summer, with surface temperature anomalies higher than for much of the globe. With few temperature station records available in this remote region prior to the 1950s, paleoclimatic data must be used to understand annual-to-centennial scale climate variability, local response to large-scale forcing mechanisms, and the significance of major features of the past millennium such as the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA) both of which can vary globally. Here we use an extensive collection of living and subfossil wood samples from temperature-sensitive trees to produce a millennial-length, validated reconstruction of summer temperatures for Mongolia and Central Asia from 931 to 2005 CE. This tree-ring reconstruction shows general agreement with the MCA (warming) and LIA (cooling) trends, a significant volcanic signature, and warming in the 20th and 21st Century. Recent warming (2000–2005) exceeds that from any other time and is concurrent with, and likely exacerbated, the impact of extreme drought (1999–2002) that resulted in massive livestock loss across Mongolia. [note other papers have blamed this upon concurrent La Nina conditions]

New paper finds eastern equatorial Pacific Ocean was 2C warmer than present 10,000 years ago

A paper published today in Earth and Planetary Science Letters finds the Eastern equatorial Pacific Ocean was ~2°C warmer than the present during the early Holocene from 10,000 to 8,000 years ago.

According to the authors, 

"Temperature estimates...show higher temperatures in the early Holocene, a cooling of ∼2° by [8,000 years before the present] and after relatively stable temperatures to the present."
and as demonstrated by graphs from the paper below:

Horizontal axis is thousands of years before the present. Graph A shows temperature proxy from Antarctic ice cores, graph B shows 0-150m depth ocean temperature in black

Contrary to popular belief, the global oceans have warmed only 0.09C (9 hundredths of one degree) over the past 55 years (Levitus et al 2012). The entirely natural warming of the Eastern Equatorial Pacific Ocean at the beginning of the Holocene ~10,000 years ago found by this paper is over 22 times greater by way of comparison. The IPCC claims irreversible, catastrophic 'tipping points' will occur from global warming of 1.5 - 2.0C, but hundreds of temperature proxy papers have demonstrated no such tipping points occurred with temperatures 1.5C up to 6C warmer many times in the past. 

Related: New paper finds the 18+ year 'pause' of global warming is not due to missing heat hiding in the deep oceans


Eastern equatorial Pacific ocean heat content is influenced by Southern Ocean dynamics.
Southern Ocean temperature signal reached the equatorial Pacific thermostad via SAMW.
Eastern Equatorial Pacific thermostad sequesters heat from the surface.

Abstract

Temperature reconstructions from a shallow core (375 m) from the Peru Margin are used to test the influence of Subantarctic Mode Water (SAMW) on the eastern equatorial Pacific (EEP) thermostad and thus the effect of southern high latitude climate on interior ocean heat content (OHC). Temperature estimates, based on Mg/Ca measurements of planktonic and benthic foraminifera (Neogloboquadrina dutertrei and Uvigerina spp ., respectively) show higher temperatures in the early Holocene, a cooling of ∼2° by 8 kyr B.P. and after relatively stable temperatures to the present. The temperature signal is similar in direction and timing to a rather robust Holocene climate signal from the southern high latitudes suggesting it originated there and was advected to the core site in the EEP. Based on the N. dutertrei and Uvigerina Mg/Ca temperature and δ13C records we conclude that SAMW acted as a conduit transporting the southern high latitude climate to the interior of the equatorial Pacific. We propose that the early Holocene warmth is related to a southward migration of the Subtropical Front, which enhanced the influence of warm subtropical water in the region of SAMW formation and was then transported to the EEP thermostad. The early Holocene warmth recorded in the EEP thermostad has a muted sea surface temperature expression indicating this mechanism is important for sequestering heat in the ocean interior.

UPDATE: Coincidentally, another paper was published today showing sea surface temperature (SST) proxies of the Western North Atlantic Ocean and North Atlantic Ocean over the past 14,000 years, both of which demonstrate higher sea surface temperatures than the present during the early and mid-Holocene: