Isn't it considered a fact that at times in earth's history the CO2 concentration has been much higher?

Question

Do we know with any certainty what the climate was like in these periods? Also did life, as a whole, struggle more or less to survive?

Answer 1

you are correct in your assertion, except to say it is 'considered a fact'.  There are several schools of thought on this subject, and there is some paleo-biologists who have suggested that, based upon the proliferation of biomass evident by oil and coal deposits, and the 'trapped air bubbles' in polar ice, and other types of ice, that there was a larger amount of CO2 in the earths atmosphere in the past than there is today...while the 'majority of scientists' may not agree, it is a viable theory, but it is only a theory, as the information gathered is not necessarily valid, due to the discrepancies in the art of dating ice samples...good question, as a side note, it has been surmised by some paleo-archeologists, that the proliferation of the indian population in the southwest part of the US, as evidenced by the large ruins of cities left by the people we now call the 'Anasazi' may have been the result of the increased rainfall and more temperate climate the 'global warming' caused in the 10th through 12 centuries...just a theory, though, no hard evidence...

Answer 2

CO2 has not increased that much. The environmentalist measure it at 380 ppm. Oxygen is 20.9% of our atmosphere. Now convert the ppm to percent and u have .000,380% . Which is nothing.In hazardous gas U always watch the oxygen as that is what U need. CO2 is not toxic but it can kill you just like it smothers out a fire.  

Answer 3

yes

Answer 4

Life got by just fine back then.

The problem we have is that life and our civilisation at present is adapted to conditions of lower CO2 concentrations and a lower global mean temperature than what existed in the past and the change to higher CO2 concentration and higher global mean temperature is going to cause us a lot of problems.

To make matters worse the current human caused global warming is happening much faster than any natural global warming event so we can't use the fact that they worked out OK as proof that there's nothing to worry about.

Answer 5

There have been mass extinctions when CO2 concentrations got too high.  

"The Permian–Triassic (P–Tr) extinction event, informally known as the Great Dying, was an extinction event that occurred 251.4 million years ago,[1] [2] forming the boundary between the Permian and Triassic geologic periods. It was the Earth's most severe extinction event, with up to 96 percent of all marine species[3] and 70 percent of terrestrial vertebrate species becoming extinct; it is the only known mass extinction of insects.[4]"

"The observed pattern of marine extinctions is also consistent with hypercapnia (excessive levels of carbon dioxide)."

Answer 6

Natural fluctuations occur and will continue to occur.  I read (i think at A USGS site) that past CO2 concentrations were 100 times higher than current, and that the enhanced warming may have help life develop on this planet at a time when solar output was very low.  This was actually before there was a lot of life on the planet.  I don't know the time scale and I'm sure the accuracy is questionable looking back so far.  I think they determined it from shells in the ocean form some microscopic critter.

However, during the past few ice ages (400,000 years of proxy data), it appears that the atmospheric CO2 concentration has been much lower than today 180 to280 ppm (see figure 2 and pages 1-3 of http://www.usgcrp.gov/usgcrp/Library/030...  The reference is a national academy paper looking at the carbon cycle posted at the US Global Change Research Program (NOAA, USGS, NASA all are a part of this).

You are absolutely correct that CO2 lags behind temperature historically.  That is a great observation and scientist have long known this.  The answer (what is thought to be correct) is that as the climate warms from natural processes (orbital effects, solar cycles), the natural decay processes increase, increasing the CO2 in the air, which in turn, increases the temperature more.  this is a positive feedback that reinforces warming. More plants grow using more CO2 and transpiring water.

As orbital and solar cycles cause cooling, decay slows because of the cold. Fewer plants also grow and transpiration is interrupted, which affects the hydrologic cycle.  CO2 historically increases following a natural warming cycle and decreases after it cools down a bit.  Scientists are very familiar with the natural process  (see http://dels.nas.edu/dels/rpt_briefs/clim... .  There is no dispute about the natural process involved with global warming.  Scientist know this. This is the basis for the GW theory.

The carbon cycle was in balance historically because growing plants used what was emitted from decay and fires.  Some carbon dioxide was "permanently" removed from the system and stored underground as fossil fuel.  No animal on earth used these resources everyday.

With the industrial revolution, humans have started to use the resource.  And we now pump billions of tons of CO2 annually into the air from the use of fossil fuels.  We are sure of the correlation between CO2 and temperature changes - we know in the past as temperature increased, more decay resulted in more CO2 was emitted and temperature increased more  - very strong relationship and no dispute.  We also know we are disrupting the carbon cycle by putting in 30-50% (?? - I can't remember the source - I may be thinking about the amount the ocean absorbs) more carbon than the ecological systems on earth can absorb - this is directly measurable.  We are now worried that correlation we have observed in the past and cause and effect.  There is every reason to think a rise in CO2 will result in a rise in temperature - pure physics and reproducible in a lab.  We know the radiative forcing ability of CO2 - very high (it should be in the references provided). We think we will cause a temperature change by pumping lots of CO2 into the air that cannot be absorbed and used by the Earth's ecosystems.  We model the impacts of the extra CO2 in the air using physics and include the natural factors that cause global warming (in references). The physics suggest this is happening.  

The predictions made in the 1992 IPCC reports (polar and high latitude temperatures rising fastest, sea ice and glaciers melting, sea level rising at and increasing rate, and air temperatures increasing at an increasing rate) and happening now.  We observe this and it is not disputed by scientists.  The temperature has risen an average of  0.7 C over the past 100 yrs and there are open waters at the poles that have never been open before in human history.  Most of the worlds glaciers are disappearing.  Humans produce billions of tons of CO2 beyond what natural process produce annually.  This is all observable and undisputed by scientists.

Answer 7

http://www.livescience.com/history/08081...

This just showed up on YA a couple of days ago. Shows dramatic climatic variation in a short period of time. Don't know what was going on with the co2.

Answer 8

Yes, CO2 concentrations have been higher in the past. When they get higher, the planet gets hotter.

The pace of evolution is not dependent on temperature (as far as we know). But here's the problem: CO2 levels haven't been this high in more than 20 million years. Almost everything you eat evolved under a different climate than the one we're heading toward. Every grain, every fruit, every mammal and bird in your own personal food chain is threatened. We're not all going to die. But a lot of us might starve.

The time lag does not refute AGW theory because we understand why the time lag occured and what caused it. In the pre-human world, large scale climate change was triggered by small changes in earth's orbit called Milankovitch cycles. These cycles start climate change, but they are far too small to explain all of the warming and cooling we observe.

http://www.sciencemag.org/cgi/content/ab...

The Milankovitch cycles are amplified by feedback mechanisms, one of which is dissolved CO2 in the ocean. Once the oceans begin giving up their CO2 -- a process that takes a few hundred years -- the pace of warming accelerates.

Lucky for us, the oceans are right now still in CO2-absorbing mode. As the planet continues to warm, they will absorb less and less. Sometime around 2100, the oceans will be warm enough that they will begin releasing into the air the CO2 they absorbed back in the 20th century.

If we don't have a good handle on our carbon emissions by that time, we're all screwed. And so is the planet.

http://www.ncbi.nlm.nih.gov/sites/entrez...

Good question. Starred.

Answer 9

Absolutely.  But a whole lot of things were different than, and it's not directly comparable.  The current level of CO2 is the highest it's been in 400,000 years, and the current temperature is the highest in several thousand years.

EVERY major scientific organization says the data proves that this particular warming is mostly caused by us.  And they know all about the levels of CO2 in the distant past.

Answer 10

Sure - Ice core samples trap the air of ancient times and gives us clues to what the climate make up was long before man.

Co2 levels were higher and lower than we see today, and temperatures were higher and lower than today as well.

But there isn't any correlation between co2 and temps, but there is a relationship between temps and co2.  The co2 levels of the climate lag behind temperature by some 800 years.

This proves that as the Sun's output increases, temperatures increase causing life to flourish which causes more co2.

Answer 11

For Bob, Dana and Ken the temperatures were higher only 70 years ago than they are currently. They were also warmer in the 1600s for a short spell and from the early 700s through the early 1300s it was noticeably warmer than even 1934.  The whole problem is the model that Hansen and the IPCC are using predicts higher temperatures while in actuality they are dropping. The disconnect comes in the early 80s when some how current temperatures were recorded world wide 5 to 10 degrees hotter than they really were. This is what NASA is now correcting and I have heard they are looking at serious jail time for the person who altered the data.

Answer 12

Bob says "The current level of CO2 is the highest it's been in 400,000 years". This is not true. You don't have to go that far back in history to answer this.

In 1944 atmospheric CO2 was measured at 415 ppm. http://personals.galaxyinternet.net/tung...

The Temperature anomaly was + 0.12 http://hadobs.metoffice.com/hadcrut3/dia...

By comparison we currently have CO2 at 384 ppm, with a temperature anomaly (July 2008) of 0.403.

In 1944 there were higher CO2 levels, but the temperature was lower. We know exactly what the weather was like then (towards the end of WW2) ... normal.

bubba... "The predictions made in 1992 " have not happened.

The Global temperature has not risen in 10 years.

http://hadobs.metoffice.com/hadcrut3/dia... (Hadcrut3)

The Ocean temperature has not risen in 10 years.

http://www.junkscience.com/MSU_Temps/NCD... (NOAA)

Sea Levels have been falling for 5 years.

http://sealevel.colorado.edu/current/sl_... (Colorado University)

Answer 13

Yes. Carbon dioxide levels have been much higher in the past. And it's no coincidence that when there was more carbon dioxide, average temperatures were higher.

Life didn't struggle to survive. Carbon dioxide isn't poisonous, it's just a greenhouse gas. The temperature changes probably caused some species to go extinct, but overall, the changes happened slowly enough to let most species evolve to match the new temperatures.

Which is why we need to be concerned now. Our coal-burning during the past few centuries has increased carbon dioxide levels at unnaturally high rates. It's too fast for evolution.

Edit. Carbon dioxide can exist in the ocean as carbonic acid. When temperatures rise, the equilibrium between carbon dioxide and carbonic acid shifts toward carbon dioxide. Thus, the oceans release carbon dioxide gas into the atmosphere. Increased carbon dioxide concentrations continue to increase temperatures which causes oceans to release more. Higher temperatures cause more CO2, and more CO2 causes higher temperatures. This - natural - cycle starts with - natural - warming, but soon accelerates.

Right now, human activities are causing increases in carbon dioxide levels, which is causing increases in temperature. The planet has been cooling -- not warming -- for the last thousand years or so, until recently. The fact that recent increases in CO2 levels and temperatures have happened without centuries of rising temperatures beforehand should prove that our current warming trend is not natural.

Answer 14

It's been warmer when CO2 levels were lower, and cooler when CO2 levels were higher.

There are other, stronger, factors influencing climate.   CO2 is not even a particularly strong greenhouse gas - "catastrophic" warming theory relies on some CO2-driven warming causing other factors to occur, with those stronger factors causing runaway warming.    Except, it's been warmer and those follow-on events didn't happen.

There have been past CO2-driven warm periods and they were materially warmer than today, but they involved CO2 levels 1200%-1500% higher than today's levels.    Not 1/3 higher.

Answer 15

A natural buildup of CO2 can be caused by massive forest fires and plant die-offs (we have that now and its happened in the past).  What we've added to the mix is what we cause.  The Earth would be able to handle the CO2 buildup from the natural causes, but we are pushing it much further and much faster than the natural system can cope with.  

One thing that concerns me almost as much as global warming is the effects of air pollution in some parts of the world.  It is not inconceivable that the pollution will turn toxic and kill whole populations overnight if it keeps up.  

Answer 16

Yes, CO2 was higher at times in the past. But it's never been higher during the entire history of homo sapiens. And our entire civilization has been built in just the past few centuries or millennium. Clearly, neither our species nor our civilizations infrastructure are particularly well suited to the climate millions of years ago.

Answer 17

Yes.  The atmospheric CO2 concentration has been much higher, as was the global temperature, and completely different species (adapted to that climate) were living on the planet.

Answer 18

bestonnet

"To make matters worse the current human caused global warming is happening much faster than any natural global warming event"

This is erroneous. Nothing about the rate of recent warming is unprecedented. It is not even all that unusual.