How do we know the temperature of the earth back 450 thousand years ago till now?

Question

And how do we know the CO2 levels back 450,000 years? How do we know the suns activity level from back about a thousand years?

Answer 1

bubbles in ice cores are only available from areas that have never thawed.

so basically we study fossil's of diatoms & other water living organisims that we know the prefered temperature ranges of.

for example 1 type will be abundant in 55 degree water, another type at 45 degrees.

we can also make estimates from fossils of larger animals such as aligators that live in a climate like florida.

there are  crocodilian teeth & an abundance of dinosaur tracks in the national oil reserve on Alaskas north slope that have been dated to 90 to 110 million years ago , so we can safely estimate the alaska climate at that time to be similar to todays florida, there are some places on earth with ice thats dated to the same period to get the composition of the atmosphere from that time.

naturally these things are never too exact, say roughly 15 degrees & 50,000 years either way. the gasses are more problematic & lead to a lot of heated chemistry discussions.

so we know great climate changes have happened in the past, as to what causes these changes, your wild azz guess is probably as good as the next guys.

if this subject interests you do some research on"paleoclimateology"

Answer 2

Core samples,both from land and sea,ice.Certain bacteria,mold, fungus,algae,microbes can be linked to certain temperature variations,giving an overview of temperature at that time period.

Answer 3

We don't, that's what I've been saying for years.

"Scientists" (not all, mind you) like to say that the Earth is warming at an alarming rate, and some say that we're causing it.

They also say that Earth is 4.5 million years old, and that certain parts of the world (Ohio, for example) was once ocean floor. How can we say what's natural and not from a 100 year temperature record?*

They say there have been Ice Ages, so there must have been nonIce Ages. Who's to say we're not just in between Ice Ages and Earth is continuing to warm.

Pluto is heating up, as well, just so you know, and that's probably our fault, too.

Answer 4

By analyzing trapped air bubbles (containing snapshots of the atmosphere when the ice was formed).  They can count the layers of ice, just like the rings in a tree, to date things.  Here's a fairly easy to understand article on the process:

http://www.csa.com/discoveryguides/iceco...

Answer 5

I have to agree with Ken on this one.  There are proxy data that can provide reasonable data to our past.

Answer 6

James Hansen of NASA's Goddard Institute for Space Studies in New York City and colleagues report that "Earth is now reaching and passing through the warmest levels in the current interglacial period" and that global temperature may be within one degree Celsius (1.8°F) of the maximum temperature of the past million years.

"That means that further global warming of 1 degree Celsius defines a critical level. If warming is kept less than that, effects of global warming may be relatively manageable," said Hansen. "During the warmest interglacial periods the Earth was reasonably similar to today. But if further global warming reaches 2 or 3 degrees Celsius, we will likely see changes that make Earth a different planet than the one we know. The last time it was that warm was in the middle Pliocene, about three million years ago, when sea level was estimated to have been about 25 meters (80 feet) higher than today."



Because of a rapid warming trend over the past 30 years, the Earth is now reaching and passing through the warmest levels seen in the last 12,000 years. This color-coded map shows how temperatures changed on average from 2001-2005. 2005 was the warmest ranked year on record. Dark red indicates the greatest warming and purple indicates the greatest cooling. Credit: NASA



Hansen said that the impact of climate change is already evident in studies that have found warmer temperatures are causing plant and animal species to migrate towards the north and south poles.

The researchers also warn that increased temperature difference between the Western and Eastern Pacific may boost the likelihood of strong El Niños, events characterized by the movement of warm surface waters in the West Pacific eastward toward South America. El Niños typically wreak weather havoc, causing severe storms in some parts of the world and devastating droughts in other regions.

A news release from NASA follows.

--------------------------------------...

NASA Study Finds World Warmth Edging Ancient Levels

A new study by NASA scientists finds that the world's temperature is reaching a level that has not been seen in thousands of years.



Image left: Data from this study reveal that the Earth has been warming approximately 0.2 degrees Celsius (0.36 Fahrenheit) per decade for the past 30 years. This rapid warming has brought global temperature to within about one degree Celsius 1.8 Degrees Fahrenheit) of the maximum estimated temperature during the past million years, when sea level was about 25 meters (82 feet) higher than today. NASA

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The study, led by James Hansen of NASA's Goddard Institute for Space Studies, N.Y., along with scientists from other organizations concludes that, because of a rapid warming trend over the past 30 years, the Earth is now reaching and passing through the warmest levels in the current interglacial period, which has lasted nearly 12,000 years. An "interglacial period" is a time in the Earth's history when the area of Earth covered by glaciers was similar or smaller than at the present time. Recent warming is forcing species of plants and animals to move toward the north and south poles.

The study used temperatures around the world taken during the last century. Scientists concluded that these data showed the Earth has been warming at the remarkably rapid rate of approximately 0.36° Fahrenheit (0.2° Celsius) per decade for the past 30 years.

"This evidence implies that we are getting close to dangerous levels of human-made pollution," said Hansen. In recent decades, human-made greenhouse gases have become the largest climate change factor. Greenhouse gases trap heat in the Earth's atmosphere and warm the surface. Some greenhouse gases, which include water vapor, carbon dioxide, methane, nitrous oxide, and ozone, occur naturally, while others are due to human activities.

The study notes that the world's warming is greatest at high latitudes of the Northern Hemisphere, and it is larger over land than over ocean areas. The enhanced warming at high latitudes is attributed to effects of ice and snow. As the Earth warms, snow and ice melt, uncovering darker surfaces that absorb more sunlight and increase warming, a process called a positive feedback. Warming is less over ocean than over land because of the great heat capacity of the deep-mixing ocean, which causes warming to occur more slowly there.

Hansen and his colleagues in New York collaborated with David Lea and Martin Medina-Elizade of UCSB to obtain comparisons of recent temperatures with the history of the Earth over the past million years. The California researchers obtained a record of tropical ocean surface temperatures from the magnesium content in the shells of microscopic sea surface animals, as recorded in ocean sediments.

One of the findings from this collaboration is that the Western Equatorial Pacific and Indian Oceans are now as warm as, or warmer than, at any prior time in the Holocene. The Holocene is the relatively warm period that has existed for almost 12,000 years, since the end of the last major ice age. The Western Pacific and Indian Oceans are important because, as these researchers show, temperature change there is indicative of global temperature change. Therefore, by inference, the world as a whole is now as warm as, or warmer than, at any time in the Holocene.

According to Lea, "The Western Pacific is important for another reason, too: it is a major source of heat for the world's oceans and for the global atmosphere."

In contrast to the Western Pacific, the researchers find that the Eastern Pacific Ocean has not shown an equal magnitude of warming. They explain the lesser warming in the East Pacific Ocean, near South America, as being due to the fact this region is kept cool by upwelling, rising of deeper colder water to shallower depths. The deep ocean layers have not yet been affected much by human-made warming.

Hansen and his colleagues suggest that the increased temperature difference between the Western and Eastern Pacific may boost the likelihood of strong El Ninos, such as those of 1983 and 1998. An El Nino is an event that typically occurs every several years when the warm surface waters in the West Pacific slosh eastward toward South America, in the process altering weather patterns around the world.

The most important result found by these researchers is that the warming in recent decades has brought global temperature to a level within about one degree Celsius (1.8°F) of the maximum temperature of the past million years. According to Hansen, "That means that further global warming of 1 degree Celsius defines a critical level. If warming is kept less than that, effects of global warming may be relatively manageable. During the warmest interglacial periods the Earth was reasonably similar to today. But if further global warming reaches 2 or 3 degrees Celsius, we will likely see changes that make Earth a different planet than the one we know. The last time it was that warm was in the middle Pliocene, about three million years ago, when sea level was estimated to have been about 25 meters (80 feet) higher than today."

Global warming is already beginning to have noticeable effects in nature. Plants and animals can survive only within certain  

Answer 7

ice cores..  something that only tells you how the temperatures were at the specific location.  Meaning they cant be used as 100% fact, and base any theories on it.  They have to match up many different proxies to formulate an ESTIMATE for that time, so its subject to bias/opinion of whoever is doing it.  There are formulas to calculate the temperatures based on the co2 and o2 isotope counts, but how do we know those air bubbles didnt get mixed when the top layer melted and refroze, or any other situation/event that could happen to the ice that might ruin the results.

Answer 8

they can count the bubbles, and all they want to count,... the problem is simple! There was an ice age many years ago.. but there was also a flood that was denied. That changes things and changes predictions! There is more evidence of the flood than an ice age.. truth is they both occurred! Earl