![]() ![]() This dark rock has many fine-grained components plus some large out-sized clasts like a modern glacial till. For ancient glaciations from the Proterozoic and Paleozoic, there are rock formations of glacial sediments such as the diamictite (or tillite) of the Mineral Fork Formation in Utah. Thus they are an indirect indicator of something like climate. A proxy indicator is a biological, chemical, or physical signature preserved in the rock, sediment, or ice record that acts like a “fingerprint” of something in the past. How do we know about past climates? Geologists use proxy indicators to understand past climate. Carrot says that this marks the first time it’s offered a discount on Premium Ultra. New Carrot users with Dark Sky installed on their iPhones can get 25 percent off the Premium Ultra subscription, or 30/year instead of 40/year. The Holocene Climatic Optimum is the warming around 6,000 years ago, though it was not universally warmer, and probably not as warm as current warming, and not at the same time everywhere. In another effort to lure Dark Sky users, Carrot is also offering a limited-time discount on subscriptions. ![]() It also is difficult to find in the Southern Hemisphere. The Younger Dryas cooling is widely recognized in the Northern Hemisphere, though the timing of the event (about 12,000 years ago) does not appear to be equal everywhere. ![]() These events are more recent and yet have conflicting information. Two of the more recent climate swings demonstrate the complexity of the changes: the Younger Dryas and the Holocene Climatic Optimum. In the last 500,000 years, there have been 5 or 6 interglacials, with the most recent belonging to our current time, the Holocene. These warming upticks are related to variations in Earth’s climate like Milankovitch cycles. Warmer portions of climate within an ice age are called interglacials, with brief versions called interstadials. X-axis is time in thousands of years (ka) so 200 is actually 200,000. \): A Pliocene‐Pleistocene stack of 57 globally distributed benthic δ18O records. ![]()
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