The big picture: 65 million years of temperature swings

Greenland Temperatures - last 10,000 years. Are we headed for an ice age? (See below for more detail.)

David Lappi is a geologist from Alaska who has sent in a set of beautiful graphs–including an especially prosaic one of the last 10,000 years in Greenland–that he put together himself (and which I’ve copied here at the top).

If you wonder where today’s temperature fits in with the grand scheme of time on Earth since the dinosaurs were wiped out, here’s the history. We start with the whole 65 million years, then zoom in, and zoom in again to the last 12,000 from both ends of the world. What’s obvious is that in terms of homo sapiens history, things are warm now (because we’re not in an ice age). But, in terms of homo sapiens civilization, things are cooler than usual, and appear to be cooling.

Then again, since T-rex & Co. vanished, it’s been one long slide down the thermometer, and our current “record heatwave” is far cooler than normal. The dinosaurs would have scoffed at us: “What? You think this is warm?”

With so much volatility in the graphs, anyone could play “pick a trend” and depending on which dot you start from, you can get any trend you want. — Jo

65 million years of cooling

The following two graphs (images created by Robert A. Rohde / Global Warming Art) are climate records based on oxygen isotope thermometry of deep-ocean sediment cores from many parts of the world [1]). On both graphs, colder temperatures are toward the bottom, and warmer temperatures toward the top. Significant temperature events on the first graph show the start and end of Antarctic glaciation 34 and 25 million years ago, and the resumption of glaciation about 13 million years ago. It is obvious from the graph that we are now living in the coldest period of Earth’s history for the last 65 million years. Despite recent rumors of global warming, we are actually in a deep freeze.

5 million years of cooling

The last five million years of climate change is shown in the next graph based on work by Lisiecki and Raymo in 2005 [2] . It shows our planet has a dynamic temperature history, and over the last three million years, we have had a continuous series of ice ages (now about 90,000 years each) and interglacial warm periods (about 10,000 years each). There are 13 (count ‘em) ice ages on a 100,000 year cycle (from 1.25 million years ago to the present, and 33 ice ages on a 41,000 year cycle (between 2.6 million and 1.25 million years ago). Since Earth is on a multi-million-year cooling trend, we are currently lucky to be living during an interglacial warm period, but we are at the end of our normal 10,000 year warm interglacial period.

The last 10 millenia

To detail the more recent prehistoric temperature changes, scientists have drilled a number of ice cores in ancient glacial ice. Paleotemperature data from ice cores is considered to be our best continuous record of temperatures on the planet for time-spans up to about 420,000 years ago. Annual layering in undisturbed glacial ice allows us to precisely date the layers, and gives us a very accurate time and temperature sequence. The US government drilled the GISP 2 ice core in central Greenland over a five-year period, and the data is available here. This data set is useful because it reports temperatures (measured by oxygen isotopes) every 10 to 60 years — a good resolution. I sometimes see graphs of ice-core temperatures or greenhouse gasses that are based on measurements every 1,000 or 2,000 years: not nearly of close enough together for comparisons that are useful today. I downloaded and graphed these data in Excel myself. The following graphs have a time scale in years Before Present (BP).

The next graph of temperature from the ice core for the last 10,000 years (the current interglacial period) shows that Greenland is now colder than for most of that period (vertical scale in degrees C below zero). We can see the Medieval Warm Period 800 to 1,000 years ago was not particularly warm, and the Little Ice Age 150 to 650 years ago was one of the longest sustained cold periods during this interglacial. We are now recovering from this abnormal cold period, and the recovery started long before anthropogenic greenhouse gases were produced in any quantity. The curved trend line in green shows that we have been experiencing declining temperatures for the past 3,000 years, and are likely to be heading down toward the next ice age. Temperatures are only considered to be increasing if viewed for the last 150 years, from 1850 onward, which is roughly when thermometers began collecting global data, and is also the period of time the UN’s Intergovernmental Panel on Climate Change (IPCC) has chosen for its review. The red portion of the curve is the recovery from the Little Ice Age. The amount of 20th century warming is unknown, since it was recently revealed that unknown portions of the international temperature databases have been tampered with, and the amount and extent of the tampering has not been publicly documented. It is likely that some warming has continued into the 20th century, but it is also likely that the amount of warming is not as great as the 0.6 degrees C that the global warming advocates would lead us to believe.

Our current warming is well within natural variation, and in view of the general decline in temperatures during the last half of this interglacial, is probably beneficial for mankind and most plants and animals. The graph clearly shows the Minoan Warming (about 3200 years ago), the Roman Warming (about 2000 years ago), and the Medieval Warm Period (about 900 years ago). Great advances in government, art, architecture, and science were made during these warmer times.

But around 65 million years ago there were massive outpourings of lava in India (see Deccan Traps). And very high CO2 levels, many times higher than today. Also the KT (”dinosaur killer”) asteroid impact occurred around that time, which also may have contributed large amounts of CO2 to the atmosphere. Again, much higher levels than we have today.

______________________________

“Greenhouse Crisis. [due to KT asteroid impact, ~65 million years ago -etl] Impact with the carbonate-rich rocks of the Gulf coast releases large amounts of CO2, initiating a greenhouse warming. Note that this would offset the proposed impact winter effects [’soot’, etc, blocking sunlight -etl].”

http://taggart.glg.msu.edu/isb200/kt.htm

______________________________

“The Deccan Traps formed between 60 and 68 million years ago,[2] at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats (near Mumbai) some 66 million years ago. This series of eruptions may have lasted fewer than 30,000 years in total.[3] The gases released in the process may have played a role in the Cretaceous–Tertiary extinction event, which included the extinction of the non-avian dinosaurs.”

http://en.wikipedia.org/wiki/Deccan_Traps#History

______________________________

“The Deccan volcanism, at 64-65 Ma: The second event of this phase is the Deccan volcanism which occurred after a hiatus of 30 Ma. Also, after exactly the same hiatus, and at the same time of 64-65 Ma, the Indian plate experienced breakup from yet another partner at Gondwanaland time – the Seychelles. This probably indicates that the second stage of magmatism, which began at 93 Ma, was controlled by the breakup events between Gondwanaland microplates and the Indian plate. Also, it shows that the breakup process was a gradual and progressive phenomenon, starting with Madagascar-India separation and, after another 30 My, Seychelles-India separation. Since this process controlled West Coast magmatism, which tectonism is expected to do, we deduce that the magmatism was also progressive. Thus, we conclude that (i) the rhyolitic volcanism at 93 Ma resulted from Madagascar-India breakup, and (ii) that this breakup event was a continuous process which led to Seychelles-India breakup after another 30 My and to Deccan volcanism at the same time. The progressive chemical trend of the volcanics, i.e., from rhyolite to basalt, indicates gradual progressive increase in temperature and/or gradual progressive lowering of the liquidus in the magma chamber as a result of gradual progressive rifting/breakup of the Indian plate with Madagascar and the Seychelles respectively.

The shift from plutonism during first phase to volcanism during the second phase perhaps indicates the presence of direct, uninterrupted conduits from the magma chamber to the surface of the continental crust during the second phase. This is what is expected during extensive rifting events such as Madagascar-India and Seychelles-India separation which did not occur during the first phase.

The large volume of the Deccan volcanics and the high rate of volcanism during the Deccan episode indicate:

1. higher rate of adiabatic decompression due to continental scale rifting,

2. consequently, higher rate of melting of magma in the chamber,

3. further, continental delamination of the western continental crust due to elevation in temperature and decrease in viscosity caused by the presence of a heat source in the form of a magma chamber at its base, and

4. a direct plumbing system between the melt and the surface, during eruption.

Considering that the West Coast and Narmada-Tapi rift zones were reactivated at the time of Deccan volcanism and the Cambay and Kutch rifts were also available as direct conduits for the upward movement of melt, we infer that the presence of these four rifts and geophysical evidence of lithosphere thinning beneath the westen coast explains the size, volume and eruption rate of the Deccan volcanics.

The geochemical variation within the Deccan volcanics, as mentioned above, perhaps indicates differences in the chemistry of the host rocks. For example, along the Narmada-Tapi rift zone the magmatic melt must have interacted with the host sediments, which are Mahakoshal Jurassics along with Archean metamorphics. Similarly along the West Coast, Cambay and Kutch rifts, the melt would have interacted with Archean-Precambrian metamorphics. Consequential changes in the chemistry would be reflected in the geochemistry of the DVP volcanics.”

http://www.mantleplumes.org/Deccan2.html

'Are we headed for an ice age?'

Simple answer, YES.

I'm a 'science junky'. It prolly has something to do with my profession where I work with the Laws of Physics everyday and 'a' + 'b' always = 'c', and 'X' x 'Y' always = 'Z'. And no guessing or 'computer modeling' is required to 'prove' that E=mc² works every time.

And as a science junky, in my spare time I watch the Science Channel like addicts chase their next fix. And the 'SC" has numerous series on the Earth and our Climate. They're directly related, climate specific, or as a byproduct of some series on our Solar System and/or Cosmology.

Long story short;

We are coming OUT of a naturally occurring warming period, and entering a naturally occurring Cooling Period. These cyles have repeated and repeated since our present Earth, ver 2.0, was created along with the moon approx 4.5 Billion years ago.
During this time we've even had periods called 'Ice Ball Earth' where the Earth was like one 'HUGH' snowball. Every spot, even at the equator, was covered in snow or ice. Scientists (real ones /s), know of one period of Ice Ball Earth' for positive and there's evidence that it may have happened twice.

So. Are we headed for an ice age? You betcha₍₁₎. Unfortunately these Real Scientists can't predict when, as in how soon, it will happen.

(1) Al Gore, please pick up the Red Courtesy Phone.

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