What was the atmospheric co2 concentration in 1900

To see precise values, hover your mouse cursor over the red and blue graph traces. However, all values are shown with about one more significant digit than is warranted by the precision of the measurements, and the ice core values are less accurate than the Mauna Loa measurements.

Click here for a downloadable, bookmarkable image or in Internet Explorer you can use PrtScn. Bollenbacher Scripps Institution of Oceanography. Atmospheric carbon dioxide measurements have been collected here daily since Pre data comes from ice core data taken from Antarctica. Historical and current atmospheric temperature can be overlayed on the graph. Learn more about the data sources. This interactive graph is free to use on your website.

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New CO2 measurement data is updated automatically every day and temperature data is updated monthly. Use your fingers to pinch and zoom on a handheld device or use a mouse with a computer. Customizable and Responsive Choose from 4 color themes to match your website's look and feel. But over a long term, say a decade, the rise was clearly as inexorable as the tides. And global temperatures began to rise again. It was getting increasingly difficult for scientists to believe that the greenhouse effect was no cause for worry.

Meanwhile global temperatures resumed their rise. The cooling from smoke particles had a limit, for the particles dropped from the atmosphere in weeks whereas the accumulating CO 2 would linger for centuries. It was getting increasingly difficult for scientists to claim that the greenhouse effect was no cause for worry. By the ever more powerful computers had confirmed that it was impossible to construct a model that could mimic the current climate and that did not warm up a few degrees if the level of the gas was doubled.

How would we know if we should take action to avert dangerous climate change? In a couple of experienced climate scientists reviewed the predictions of the best computer models, and compared them with the natural fluctuations of climate observed in the past. Concerns were sharpened by new evidence from holes arduously drilled into the Greenland and Antarctic ice caps.

The long cylinders of ice extracted by the drills contained tiny bubbles with samples of ancient air — by good fortune there was this one thing on the planet that preserved CO 2 intact.

Group after group cut samples from cores of ice in hopes of measuring the level. For two decades, every attempt failed to give consistent and plausible results. Finally reliable methods were developed. The trick was to clean an ice sample scrupulously, crush it in a vacuum, and quickly measure what came out.

In , a team published findings that were definite, unexpected, and momentous. These Greenland measurements were later called into question, but the dramatically lower ice-age level was quickly confirmed by other studies.

When scientists get the same numbers using utterly different methods, they begin to feel that they have touched reality.. The Vostok core, an ice driller declared, "turned the tide in the greenhouse gas controversy. All through these decades, a few geologists had continued to pursue the original puzzle raised by Tyndall and Chamberlin — had changes of CO 2 been responsible for the greatest of climate changes?

These were the vast slow swings, lasting tens of millions of years, between eras like the age of dinosaurs with summer-like climates almost from pole to pole, and eras like our own when continental ice caps waxed and waned. There was no consensus about the causes of these grand shifts, and nobody had found a way to reliably measure the atmosphere many millions of years back.

Nevertheless, by the s, scientists turned up evidence suggesting that CO 2 levels had been elevated during the great warm eras of the past. Lines of thinking converged to emphasize the importance of the greenhouse effect. Geologists had been puzzled for decades by a calculation that astrophysicists insisted was indisputable: billions of years ago the Sun had been dimmer, and had gradually grown brighter as it consumed its nuclear fuel.

In the distant past the oceans should have been frozen entirely. Yet somehow the Earth's temperature had remained neither too cold nor too hot to sustain life. The best guess was that CO 2 acted as a thermostat for the planet. Volcanoes presumably put the gas into the atmosphere at a fairly constant rate. In the earliest times there could have been enough greenhouse gases to keep the planet unfrozen. But chemical processes run faster at higher temperatures, so as the Sun grew brighter the weathering of rocks would take up CO 2 faster.

As the rocks eroded, rivers carried the soil into the seas, where the carbon eventually wound up in compounds deposited on the seabed.

Thus a rough self-sustaining balance would be maintained among the forces of solar radiation, volcanic emissions, greenhouse warming, weathering, and ocean uptake. To be sure, if there was some great disturbance the system might take millions of years to stabilize.

Such great disturbances — even a totally glaciated "snowball Earth" — were not a fantasy of oversimplified models. Geologists turned up evidence that more than half a billion years ago the oceans had actually frozen over, if not entirely then mostly. That seemed impossible, for how could the Earth have escaped the trap and warmed up again?

There was at least one obvious way but it was only obvious once someone thought of it, which took some years. Over many thousands of years, volcanoes would have continued to inject CO 2 into the atmosphere. There the gas would have accumulated, since it could not get into the frozen seas. Eventually a colossal greenhouse effect might have melted the ice. The planet Venus, on the other hand, seemed to have suffered a runaway greenhouse catastrophe: a surface that might once have been only a little warmer than the Earth's had heated up enough to evaporate the carbon in the rocks into the atmosphere while ever more CO 2 was created, making the planet a hellish furnace.

All this was speculative, and proved little about our future climate. But it added to the gathering conviction that CO 2 was the very keystone of the planet's climate system — a system by no means as cozily stable as it appeared. Another unusual disturbance had begun. And the drill was still only partway down; by the time they stopped drilling a dozen years later, the team had recovered ice going back , years, through four complete glacial cycles.

The CO 2 levels in their record got as low as parts per million in the cold periods and reached in the warm periods, never higher. But in the air above the ice, the level of the gas had reached — far above anything seen in this geological era and still climbing.

Level of CO 2 in the atmosphere, The curve has been climbing exponentially, much faster now than in the s. Despite some attempts to slow down emissions, the quantity of gas added to the atmosphere is doubling every years. During the s, further ice core measurements indicated that at the end of the last glacial period, the initial rise of temperature in Antarctica had preceded CO 2 changes by several centuries.

Scientists debated whether the dates could be measured so precisely, but certainly around Antarctica the temperature rise had not come much after the rise of CO 2. But in fact the discrepancy was not good news. It seemed that rises or falls in carbon dioxide levels had not initiated the glacial cycles.

In fact most scientists had long since abandoned that hypothesis. In the s, painstaking studies had shown that subtle shifts in our planet's orbit around the Sun called "Milankovitch cycles" matched the timing of ice ages with startling precision. The amount of sunlight that fell in a given latitude and season varied predictably over millenia. As some had pointed out ever since the 19th century, in times when sunlight fell more strongly on northern latitudes in the spring, snow and sea ice would not linger so long; the dark earth and seawater would absorb more sunlight, and get warmer.

However, calculations showed that this subtle effect should cause no more than a small regional warming. How could almost imperceptible changes in the angle of sunlight cause entire continental ice sheets to build up and melt away? The new ice cores suggested that a powerful feedback amplified the changes in sunlight. The crucial fact was that a slight warming would cause the level of greenhouse gases to rise slightly.

For one thing, warmer oceans would evaporate out more gas. For another, as the vast Arctic tundras warmed up, the bogs would emit more CO 2 and another greenhouse gas, methane, also measured in the ice with a lag behind temperature.

The greenhouse effect of these gases would raise the temperature a little more, which would cause more emission of gases, which would Many thousands of years later, the process would reverse when the sunlight falling in key latitudes weakened. Bogs and oceans would absorb greenhouse gases, ice would build up, and the planet would slide back into an ice age.

This finally explained how tiny shifts in the Earth's orbit could set the timing of the enormous swings of glacial cycles. Or, more ominously, how a change in the gas level initiated by humanity might be amplified through a temperature feedback loop.

The ancient ice ages were the reverse of our current situation, where humanity was initiating the change by adding greenhouse gases. As the gas level rose, temperature would rise with a time lag — although only a few decades, not centuries, for the rates of change were now enormously faster than the orbital shifts that brought ice ages.

There were many ways temperature or other climate features could influence the carbon dioxide level one way or another. Perhaps variations of temperature and of weather patterns caused land vegetation to release extra CO 2 , or take it up Into the 21st century, scientists kept finding new ways that warming would push more of the gas into the atmosphere. As one of them remarked, "it is difficult to explain the demise of the ice sheets without the added heating from CO A key point stood out.

The cycling of carbon through living systems was not something to trifle with. In the network of feedbacks that made up the climate system, CO 2 was a main driving force. This did not prove by itself that the greenhouse effect was responsible for the warming seen in the 20th century. And it did not say how much warming the rise of CO 2 might bring in the future.

What was now beyond doubt was that the greenhouse effect had to be taken very seriously indeed. By now there were a dozen teams around the world using computers to integrate every advance in observation or theory. As the 21st century arrived, the growing agreement among the rival teams, and the consistency of their models' results with many different kinds of observations, became overwhelmingly convincing.

No model that could simulate the Earth's climate — and some of the simulations had become very good indeed — failed to show warming if its greenhouse gas level was raised. Scarcely any expert with a record of contributing to climate science now doubted that CO 2 and other greenhouse gases were at least partly responsible for the unprecedented warming all around the world since the s.

A final nail in the coffin of scientific skepticism came in , when a team compiled accurate long-term measurements of temperatures in all the world's ocean basins.

It was not in the air but the massive oceans, after all, that most of any heat added would soon wind up. Indeed natural fluctuations had kept air temperatures roughly the same since the late s; the significant question was whether the oceans were continuing to warm.

The team found that over many decades the planet's content of heat-energy had been rising, and was rising still this continued steadily after as well. There was only one remotely plausible source of the colossal addition of energy: the Earth must be taking in more energy from sunlight than it was radiating back into space. Simple physics calculated that to heat all that seawater required nearly an extra watt per square meter, averaged over the planet's entire surface, year after year.

The number was just what the elaborate greenhouse effect computations had been predicting for decades. James Hansen, leader of one of the studies, called the visible increase of the planet's heat content a "smoking gun" proof of greenhouse effect warming see graph below. Moreover, in each separate ocean basin there was a close match between the pattern of rising temperatures measured at each location and depth and detailed model calculations of where the greenhouse effect warming should appear.

Warming from other sources, for example a change in the Sun's output, could not produce these patterns. Evidently the modelers were on the right track. Yet amid all the uncertainties about how carbon cycles operated, how much could we trust the computer models to work under circumstances different from the present?

Scientists are more likely to believe something if they can confirm it with entirely independent lines of evidence, preferably from somewhere nobody had looked before. Just such new evidence came up in the s, thanks to an unexpected alliance of paleontology and plant physiology. Studies of plant species that had changed little since the rise of the dinosaurs magnolia for one showed that if you exposed them to a higher level of CO 2 , the structure of their leaves changed.

Ancient fossil leaves showed just such changes. Several kinds of chemical studies of ancient rocks and soils helped pin down how the level of the gas had swung widely over geological ages, and the temperature too. A sustained effort by many geochemists and their allies managed to get numbers for the "climate sensitivity" in past eras, that is, the response of temperature to a rise in the CO 2 level.

Not only during the recent ice ages but back over hundreds of millions of years under radically different conditions, a doubled level of the gas had always gone along with a temperature rise of three degrees, give or take a degree, in full agreement with the computer calculations. It was reassuring that there seemed scant possibility of a Venus-style runaway greenhouse apocalypse. It was less reassuring to see what the climate had looked like in the ancient eras when CO 2 had stood at a high level — a level that humanity would eventually reach if we went on burning all available oil and coal.

The Earth had been virtually a different planet, with tropical forests near the poles and sea levels a hundred meters higher. To be sure, it would take many thousands of years to melt entire polar ice caps. But in the meantime even a modest sea-level rise would disrupt humanity's teeming coastal populations. If humanity's emissions continued they seemed bound to bring not only "a warming unprecedented in the past million years," as one of many worried scientists explained, but changes "much faster than previously experienced by natural ecosystems By , new studies had pinned down some truly disturbing numbers about eras in the distant past when CO 2 levels had been high — although no higher than we would reach by the late 21st century if emissions continued to rise without restriction.

In those eras global temperatures had been at least three degrees higher than at present, and perhaps as much as six degrees higher, that is, in the upper range of what computer models found plausible, if not higher still. For the real planet, a rise in temperature had evidently not been limited by increased cloud reflection or the like. The rise had instead apparently been amplified by positive feedbacks, as ice and oceans and vegetation responded over centuries to the changing conditions with darker surfaces and their own gas emissions.

The computer models did not take these slow feedback loops into account. Hansen and others argued that humanity risked setting off a chain reaction that would eventually bring an altogether catastrophic planetary change. In the first decade of the 21st century international panels of experts reviewed the evidence, and announced conclusions that were checked and endorsed by virtually all the major national science academies, scientific societies, government science agencies and other bodies representative of scientific expertise.

All of these bodies declared that the world faced a serious problem, andrecommended that governments adopt strict policies to restrict greenhouse gas emissions. All, that is, except a few self-appointed panels composed primarily of people with limited expertise in climate science, representing ideological and business interests that opposed all forms of government regulation. Of course they continued to argue vehemently over details, as always in frontier research.

Critics pounced on every apparent discrepancy. They published long lists of scientists who denied there was any problem — although the lists included hardly any scientist who had made significant contributions to climate research.

Through all these discoveries and controversies, Keeling and his colleagues had kept on quietly monitoring and analyzing the ongoing changes in atmospheric CO 2 levels. Since the s, a cooperative international program had been measuring the gas at land stations around the world and along shipping lanes.

The baseline continued to rise ominously, but not smoothly. There had been years when the world's atmosphere had gained one billion metric tonnes of the gas, while in other years it gained as much as six billion.

How much did changes in the world's industries and agricultural practices affect the rate of the rise? Economic statistics allowed a good reckoning of how much gas humanity emitted in burning fossil fuels — and also of some significance, in the manufacture of cement — but the effects of deforestation and other land use changes were not so easy to figure.

How much did changes in the level of CO 2 reflect changes in the growth or decay of plants, perhaps related to climate fluctuations? Most of the "missing" carbon was finally located, with gradually increasing precision, in rapidly changing forests and forest soils, along with other biological reservoirs.

Another marker of biological activity was the rare isotope carbon Plants take less of it from the atmosphere than the lighter isotope carbon, so the latter is over-represented in coal and oil.

The fraction of the lighter isotope in the air was increasing, proving to a lingering band of skeptics that the rise in CO 2 came from humanity's use of fossil fuel, not from a mineral source such as volcanoes.

The 21st century brought a grand expansion of studies of the way CO 2 was accumulating in the atmosphere, and where the carbon went in the land and oceans. Here as elsewhere in climate research, the global scope and complexity of the problem called forth massive international projects. At thousands of locations instruments measured air, soils, trees, seawater, and more, providing "ground truth" for satellites that scanned the entire planet.

Meanwhile the level of CO 2 in the air kept rising, indeed faster than anyone had expected. Over the half-century up to , emissions of CO 2 had quadrupled. Efforts to reduce use of fossil fuels did have an effect, and by global emissions reported by national authorities were rising more slowly.

Of course even with a steady level of human emissions CO 2 would continue to accumulate rapidly in the atmosphere.

For decades the rise had in fact been accelerating, perhaps because natural systems were not absorbing carbon efficiently. In this essay we have seen how, ever since the late s, an increasing number of experts predicted that effects on climate would become clearly visible around the year They were right.

As the 21st century began, the global temperature was soaring in a way never seen before. The rise in surface air temperature was irregular, but the oceans, where most of the heat energy was stored, warmed up steadily.

Worse, field evidence showed that the expected feedbacks were kicking in. The world's plants were taking up more CO 2 , but their capacity to absorb was waning. Warmer oceans were absorbing less CO 2 , and gas was seen bubbling from melting Arctic tundra.

In sum, global warming was leading to more greenhouse emissions, which would lead to more warming Starting around some scientists began to warn that these changes were coming on faster than the international panels had predicted. Also as predicted only sooner, the world was beginning to suffer historically unprecedented heat waves, droughts, floods and storms. The sea level was rising while mountain glaciers, the Greenland and Antarctic ice sheets, and Arctic sea ice melted back, all at accelerating rates.

Important ecosystems from alpine meadows to coral reefs were showing signs of stress. For the scientists, as one of them remarked, "Seeing their own predictions come true has been a frightening experience.

Still more sobering, people were scarcely coming to grips with a fact that scientists had known for decades — the climate system has a built-in inertia. Even if emissions could magically be brought immediately to zero, the planet's' uptake of CO 2 was so slow that the gas already in the air would mostly stay there and keep the planet warm for a very long time.

For example, in a milestone US National Academy of Sciences report, Keeling and a colleague reported that a decline of the level of CO 2 in the atmosphere would take centuries. But scientists had rarely emphasized this to the public, and many people assumed that if emissions could be reined in the problem would be solved. The massive emissions were transforming the entire global carbon system into a new state.

For decades experts like Hansen had warned that global temperature would not decline once emissions ceased — there might indeed be feedbacks that would make for more warming.