Later On

A blog written for those whose interests more or less match mine.

Search Results

Think of the total amount of CO2 emitted by burning (coal and oil and natural gas) since 1751. What percentage of that was during your own lifetime?

leave a comment »

Written by LeisureGuy

4 March 2021 at 2:12 pm

Exxon Predicted 2019’s Ominous CO2 Milestone in 1982

leave a comment »

But they kept quiet about it. Brian Kahn reports in Gizmodo:

Atmospheric carbon dioxide sets a new record every year. This year’s cracked the ominous milestone of 415 parts per million (ppm) thanks to ever rising emissions from human activities. The sharp rise might seem like something nobody could’ve predicted but there’s at least one group of scientists that were on the money 37 years ago: Exxon’s ace team of scientists.

Internal memos unearthed in InsideClimate’s Pulitzer-winning 2015 investigation into the company revealed all sorts of solid science being done even as the oil giant sowed doubt in public. Bloomberg reporter Tom Randall revisited the memos in light of the world’s new carbon dioxide milestone and tweeted a graph from one showing just how much Exxon knew what our future would look like.

It’s eerie seeing how well the company understood both climate science and the world’s patterns of economic growth built on the back of fossil fuels. Here’s that chart, annotated for ease of reading:


Red lines show where Exxon thought the world’s carbon dioxide levels and temperatures would be at around 2019.Image: InsideClimate News

The prediction is a pretty damn good one. The world is now about 1 degree Celsius (1.8 degrees Fahrenheit) warmer than it was and carbon dioxide levels are at 415 ppm. The estimate was part of Exxon’s “high case” scenario, which assumed fossil fuel use would quicken and that the world would be able to tap new reserves in the late 2000s from at the time unreachable shale gas. The memo also warned that the extra carbon dioxide would enhance the greenhouse effect and that an “increase in absorbed energy via this route would warm the earth’s surface causing changes in climate affecting atmospheric and ocean temperatures, rainfall patterns, soil moisture, and over centuries potentially melting the polar ice caps.” . . .

Continue reading.

Written by LeisureGuy

15 May 2019 at 1:21 pm

Higher CO2 levels increase crop yields, decrease crop nutrients

leave a comment »

Written by LeisureGuy

9 May 2014 at 10:42 am

Posted in Food, Global warming

New: A greenhouse gas 7,000 times more effective than CO2

leave a comment »

Methane has been a big worry: lots of it trapped in the tundra, now boiling off over the summers. Methane (CH4) is 25 times more warming than CO2, and Nitrous Oxide (N2O) is 298 times more warming than CO2. But Suzanne Goldenberg brings us some bad news in The Guardian:

A new greenhouse gas that is 7,000 times more powerful than carbon dioxide at warming the Earth has been discovered by researchers in Toronto.

The newly discovered gas, perfluorotributylamine (PFTBA), has been in use by the electrical industry since the mid-20th century.

The chemical, that does not occur naturally, breaks all records for potential impacts on the climate, said the researchers at the University of Toronto’s department of chemistry.

“We claim that PFTBA has the highest radiative efficiency of any molecule detected in the atmosphere to date,” said Angela Hong, one of the co-authors.

The study, published in the journal Geophysical Research Letters, found PFTBA was 7,100 times more powerful at warming the Earth over a 100-year time span than CO2.

Concentrations of PFTBA in the atmosphere are low – 0.18 parts per trillion in the Toronto area – compared to 400 parts per million for carbon dioxide. So PFTBA does not in any way displace the burning of fossil fuels such as oil and coal as the main drivers of climate change.

Dr Drew Shindell, a climatologist at Nasa’s Goddard Institute for Space Studies, said:

“This is a warning to us that this gas could have a very very large impact on climate change – if there were a lot of it. Since there is not a lot of it now, we don’t have to worry about it at present, but we have to make sure it doesn’t grow and become a very large contributor to global warming.”.

He said a number of recent studies had drawn attention to other potential new greenhouse gases which, like PFTBA, pack a lot of warming potential in each molecule but are not very prevalent in the atmosphere.

Such studies were a warning against increasing uses of such compounds without first understanding their impact on climate change, he added.

“From a climate change perspective, individually, PFTBA’s atmospheric concentration does not significantly alert the phenomenon of climate change,” Hong said. “Still the biggest culprit is CO2 from fossil fuel emissions.”

But PFTBA is long-lived. The Toronot researchers estimated PFTBA remains in the atmosphere for about 500 years, and unlike carbon dioxide, that is taken up by forests and oceans, there are no known natural “sinks” on Earth to absorb it.

“It is so much less than carbon dioxide, but the important thing is on a per molecule basis, it is very very effective in interacting with heat from the Earth,” she said. “Individually each molecule is able to affect the climate potentially and because its lifetime is so long it also has a long-lasting effect.”

Hong said the discovery of PFTBA and its warming potential raises questions about the climate impacts of other chemicals used in industrial processes. . .

Continue reading.

Written by LeisureGuy

12 December 2013 at 12:49 pm

Posted in Global warming

Energy-efficient rooms, CO2, and decision-making

leave a comment »

Interesting article in Science News by Janet Raloff:

Carbon dioxide has been vilified for decades as a driver of global warming. A new study finds signs that CO2, exhaled in every breath, can exert an equally worrisome threat — impaired cognition — in nearly every energy-efficient classroom, meeting hall or office space.

The work assessed decision-making in 22 healthy young adults. Their performance on six of nine tests dropped notably when researchers raised indoor carbon dioxide levels to 1,000 parts per million from a baseline of 600 ppm. On seven tests, performance fell substantially more when the room’s CO2was boosted to 2,500 ppm, scientists report in a paper to be published in Environmental Health Perspectives.

These data are surprising, says Roger Hedrick of Architectural Energy Corp. in Boulder, Colo., because “1,000 ppm of CO2 used to be considered a benchmark of good ventilation.” Hedrick, an environmental engineer, chairs the committee that drafts commercial ventilation standards through the American Society of Heating, Refrigerating, & Air-Conditioning Engineers.

Carbon dioxide levels are often substantially higher in buildings than the 350 to 400 ppm typically found outdoors. Indoor values of 600 ppm are considered very good. But depending on how many people inhabit a room and how many times per hour its air is exchanged with outdoor air through ventilation, “there are plenty of buildings where you could easily see 2,500 ppm of CO2 — or close to it — even with ventilation designs that are fully compliant with current standards,” Hedrick says.

“We’ve seen higher CO2 levels associated with increased student absences and poorer performances on school-type tasks,” says study coauthor William Fisk of Lawrence Berkeley National Laboratory in California. “But we never thought CO2was actually responsible. We assumed it was a proxy for other [pollutants].”

His group recruited college students to spend much of a day in a room with computers. Individuals could read or do what they wanted for much of the time. But for part of each 2.5-hour period, participants completed role-playing tests on a computer that required them to manage an organization as it underwent a series of problems or crises. Throughout each of three test segments, conducted in random order, room ventilation was kept very high. Only carbon dioxide levels varied by segment: 600 ppm, 1,000 ppm or 2,500 ppm.

The role-playing tests are more complicated than most used to measure cognitive abilities, notes epidemiologist and coauthor Mark Mendell of Lawrence Berkeley. But they offer a gauge of important real-world skills, he says. “And the magnitude of effects measured at 2,500 ppm was astonishing — so astonishing that it was almost hard to believe,” he says. . .

Continue reading.

Written by LeisureGuy

17 October 2012 at 8:18 am

A counterattack on atmospheric CO2

leave a comment »

An idea that might buy us a little more time, though so far I’ve not seen any real movement toward reducing carbon release—e.g., no carbon tax. Still, any good news is welcome. Hayley Dunning writes a feature article in The Scientist that begins:

Great blooms of oceanic algae, called phytoplankton, take carbon out of the atmosphere during photosynthesis, much of which is then taken deep into ocean with them when they die. Scientists have theorized that this mechanism helped cool the earth during historic ice ages by removing carbon dioxide from the atmosphere and storing it at the ocean floor, where it cannot be recycled back into the atmosphere. Inducing algal blooms on a large scale could do the same today, reducing the impact of carbon dioxide on the greenhouse effect and slowing the impact of global climate change.

Indeed, as reported today (July 18) in Nature, scientists have seeded the ocean with iron and watched as the resulting bloom flourished, then died, sinking down to the deep ocean with a significant amount of carbon in tow.

“[The authors] were focused and quite successful at seeing if you added iron, what would be the biological response of the phytoplankton? What was the fate of the carbon and nutrients they sucked up?” said marine geochemist Ken Buesseler of the Woods Hole Oceanographic Institution, who was not involved in the study. “This is probably the best example of a group that stayed out long enough and looked deep enough to see if there were any effects below the surface.”

During glacial periods, more dust rich in iron, an essential nutrient for algae, reaches the oceans. Iron is particularly limiting in the Southern Ocean, and previous studies have shown that adding iron to the surface waters does induce large blooms of algae. In 2004, . . .

Continue reading.

Written by LeisureGuy

19 July 2012 at 8:40 am

Measuring atmospheric CO2

leave a comment »

Fascinating long profile of the scientist who has provided the best long-term measurements of atmospheric CO2 by Justin Gillis in the NY Times:

MAUNA LOA OBSERVATORY, Hawaii — Two gray machines sit inside a pair of utilitarian buildings here, sniffing the fresh breezes that blow across thousands of miles of ocean.

They make no noise. But once an hour, they spit out a number, and for decades, it has been rising relentlessly.

The first machine of this type was installed on Mauna Loa in the 1950s at the behest of Charles David Keeling, a scientist from San Diego. His resulting discovery, of the increasing level of carbon dioxide in the atmosphere, transformed the scientific understanding of humanity’s relationship with the earth. A graph of his findings is inscribed on a wall in Washington as one of the great achievements of modern science.

Yet, five years after Dr. Keeling’s death, his discovery is a focus not of celebration but of conflict. It has become the touchstone of a worldwide political debate over global warming.

When Dr. Keeling, as a young researcher, became the first person in the world to develop an accurate technique for measuring carbon dioxide in the air, the amount he discovered was 310 parts per million. That means every million pints of air, for example, contained 310 pints of carbon dioxide.

By 2005, the year he died, the number had risen to 380 parts per million. Sometime in the next few years it is expected to pass 400. Without stronger action to limit emissions, the number could pass 560 before the end of the century, double what it was before the Industrial Revolution.

The greatest question in climate science is: What will that do to the temperature of the earth?

Scientists have long known that carbon dioxide traps heat at the surface of the planet. They cite growing evidence that the inexorable rise of the gas is altering the climate in ways that threaten human welfare.

Read the rest of this entry »

Written by LeisureGuy

25 December 2010 at 9:41 am

EPA’s responses to comments about regulation of CO2 as part of the Clean Air Act

leave a comment »

The EPA has published its responses to comments about the action it is taking in the face of global warming:

Response to Comments

EPA’s response to public comments received on the Proposed Findings and accompanying Technical Support Document may be found here:

The responses are clear and convincing (to my eye), but I’m sure that there will be some who will not be convinced and may indeed be incapable of being convinced.

Written by LeisureGuy

10 April 2010 at 9:43 am

What CO2 level would cause the Greenland ice sheet to collapse?

with 4 comments

John Cook at Skeptical Science:

A matter of concern is the potential instability of the Greenland and Antarctic ice sheets. If the Greenland ice sheet was to completely collapse, it would contribute as much as 7 metres sea level rise. Similarly, the West Antarctic ice sheet would contribute around 6 metres sea level rise. East Antarctica would contribute 70 metres of sea level rise but is less prone to collapse. Consequently, how these ice sheets respond to warming temperatures is a crucial area of research. A new paper (Stone 2010) has been published that estimates that the CO2 level that will lead to collapse of the Greenland ice sheet is between 400 to 560 parts per million (ppm). At our current rate, we should pass 400 ppm within 10 years.

While there are uncertainties over the specifics of ice sheet behaviour, there are several lines of independent evidence that paint a consistent picture of how ice sheets will respond to global warming. Focusing on Greenland, what do observations tell us has been happening to the Greenland ice sheet? Satellites use gravity data to measure the total mass balance and have found the ice sheet is …

Continue reading.

Written by LeisureGuy

22 March 2010 at 4:54 pm

CO2 levels during the late Ordovician

leave a comment »

The Ordovician has been used by denialists: high CO2 levels while also glaciation. John Cook explains:

One argument used against the warming effect of carbon dioxide is that millions of years ago, CO2 levels were higher during periods where large glaciers formed over the Earth’s poles. This argument fails to take into account that solar output was also lower during these periods. The combined effect of sun and CO2 show good correlation with climate (Royer 2006). The one period that until recently puzzled paleoclimatologists was the late Ordovician, around 444 million years ago. At this time, CO2 levels were very high, around 5600 parts per million (in contrast, current CO2 levels are 389 parts per million). However, glaciers were so far-reaching during the late Ordovician, it coincided with one of the largest marine mass extinction events in Earth history. How did glaciation occur with such high CO2 levels? Recent data has revealed CO2 levels at the time of the late Ordovician ice age were not that high after all.

Past studies on the Ordovician period calculated CO2 levels at 10 million year intervals. The problem with such coarse data sampling is the Ordovician ice age lasted only half a million years. To fill in the gaps, a 2009 study examined strontium isotopes in the sediment record (Young 2009). Strontium is produced by rock weathering, the process that removes CO2 from the air. Consequently, the ratio of strontium isotopes can be used to determine how quickly rock weathering removed CO2 from the atmosphere in the past. Using strontium levels, Young determined that during the late Ordovician, rock weathering was at high levels while volcanic activity, which adds CO2 to the atmosphere, dropped. This led to CO2 levels falling below 3000 parts per million which was low enough to initiate glaciation – the growing of ice sheets.

Last week, another study headed by Seth Young further examined this period by extracting sediment cores from Estonia and Anticosti Island, Canada (Young 2010). The cores were used to construct a sequence of carbon-13 levels from rocks formed during the Ordovician. This was used as a proxy for atmospheric CO2 levels, at a much higher resolution than previous data. What they found was consistent with the strontium results in Young 2009 – CO2 levels dropped at the same time that sea surface temperatures dropped and ice sheets expanded. As the ice sheets grew to cover the continent, rock weathering decreased. This led to an increase in atmospheric CO2 which caused global warming and a retreat of the glaciers.

Thus arguments that Ordovician glaciation disproves the warming effect of CO2 are groundless. On the contrary, the CO2 record over the late Ordovician is entirely consistent with the notion that CO2 is a strong driver of climate.

Also worth noting in the comments to that post:

Can someone please give the real scientific explanation why CO2 drives global warming? Correlation does not guarantee cause. Put CO2 in a large glass chamber and measure the change in the rate of heat dissipation compared to nitrogen and it will not alter the rate of heat transference. Can someone create a valid scientific experiment to prove or disprove this?   Thanks.

Response: The first scientific experiment proving the warming effect of carbon dioxide was conducted in 1861 when John Tyndal published laboratory results identifying carbon dioxide as a greenhouse gas that absorbed heat rays (longwave or infrared radiation). Since then, the absorptive qualities of carbon dioxide have been more precisely quantified by decades of laboratory measurements (Herzberg 1953, Burch 1962,Burch 1970, etc).

Of course, there’s no substitute for measurements made in the real world. Satellites have measured less infrared radiation escaping to space at the same wavelengths absorbed by greenhouse gases (Harries 2001, Griggs 2004, Chen 2007). The authors concluded this was "direct experimental evidence for a significant increase in the Earth’s greenhouse effect".

In science, the only thing better than direct measurements are multiple sets of independent measurements finding the same thing. Surface measurements also find an increase of infrared radiation heading back down towards Earth, confirmation of an enhanced greenhouse effect (Philipona 2004, Puckrin 2004, Wild 2008, Wang 2009). A close analysis of the downward infrared spectrum finds more energy coming back down at the same absorptive wavelengths of carbon dioxide and other greenhouse gases, thus concluding "this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming." (Evans 2006)

Written by LeisureGuy

12 March 2010 at 10:54 am

Visual depictions of CO2 levels and CO2 emissions

leave a comment »

Those whose minds are still open (and are willing to click a link) will find this post of interest, particularly the visuals.

Written by LeisureGuy

18 February 2010 at 11:21 am

Interesting: An explanation of why CO2 has lagged behind temperature change

leave a comment »

The lag in the past between warming and the rise of CO2 levels has many denialists confused, and has convinced them that warming causes the CO2 rise, not the reverse. Of course, warming can indeed cause CO2 levels to rise, but increased CO2 levels (particularly the levels we have today) definitely cause warming: the science on that is over a century old, well established and not open to informed doubt (though, of course, can be doubted by any idler with not a notion of science). This post explains the situation (with good graphs). The post’s conclusion:

To claim that the CO2 lag disproves the warming effect of CO2 displays a lack of understanding of the processes that drive Milankovitch cycles. A review of the peer reviewed research into past periods of deglaciation tells us several things:

  • Deglaciation is not initiated by CO2 but by orbital cycles

  • CO2 amplifies the warming which cannot be explained by orbital cycles alone

  • CO2 spreads warming throughout the planet

Written by LeisureGuy

9 January 2010 at 1:05 pm

"But human-generated CO2 is much less than naturally occurring CO2"

with 11 comments

The above argument is frequently made. It’s true, but so what?

Here’s the argument as framed by skeptics, with the figures showing gigatonnes per year.

Carbon_Cycle_emissions

Somehow, the skeptics stop at that point. But if they went just one step further:

Carbon_Cycle

29+439+332 emitted, 450+338 absorbed. That is, 800 gigatonnes emitted each year, 788 absorbed, leaving 12 gigatonnes per year accumulating in the atmosphere.

If you want the details, sources, and corroboration, read the entire post.

Written by LeisureGuy

29 December 2009 at 11:45 am

Oceans, about CO2: "No more for me, I’m full"

leave a comment »

Christine Dell’Amore at National Geographic News:

The world’s oceans, which normally gobble up carbon dioxide, are getting stuffed to the gills, according to the most thorough study to date of human-made carbon in the seas.

Between 2000 and 2007, as emissions of the potent greenhouse gas carbon dioxide skyrocketed, the amount of human-made carbon absorbed by the oceans fell from 27 to 24 percent.

In terms of ocean processes, “that’s a pretty large drop, and the trend is pretty clear: The ocean can’t keep up with [human-made carbon],” said study leader Samar Khatiwala, an oceanographer at Columbia University’s Lamont-Doherty Earth Observatory.

Khatiwala is careful to point out that the total uptake of carbon is not declining—the rate is just not growing as fast as it used to.

But if the oceans continue to be overwhelmed by carbon, more of the gas will remain in the already warming atmosphere, the authors say. (See global warming fast facts.)

“Ultimately the ocean is what’s controlling what’s going on here,” said Chris Sabine, a supervisory oceanographer at NOAA’s Pacific Marine Environmental Laboratory in Seattle, Washington, who was not involved in the research.

“It’s a big deal that it’s becoming less efficient in taking up CO2.”

Continue reading.

UPDATE: More info here.

Written by LeisureGuy

19 November 2009 at 9:49 am

CO2 in the past

with 6 comments

Very good post at Skeptical Science. From the post:

… So we see that comparisons of present day climate to periods 500 million years ago need to take into account the fact that the sun was 4% less active than now. What about times closer to home? The most recent period when CO2 levels were as high as today was around 15 million years ago, during the Middle Miocene. CO2 levels were at about 400 ppm. What was the climate like at the time? Global temperatures were 5 to 10 degrees Fahrenheit higher than they are today. Sea level was approximately 75 to 120 feet higher. There was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland. The close coupling between CO2 and climate led the author to conclude that "geological observations that we now have for the last 20 million years lend strong support to the idea that carbon dioxide is an important agent for driving climate change throughout Earth’s history."  (Tripati 2009).

To sum up, Dana Royer says it best: "the geologic record contains a treasure trove of ‘alternative Earths’ that allow scientists to study how the various components of the Earth system respond to a range of climatic forcings." Past periods of higher CO2 do not contradict the notion that CO2 warms global temperatures. On the contrary, they confirm the close coupling between CO2 and climate.

Written by LeisureGuy

30 October 2009 at 11:09 am

Why the focus on CO2

leave a comment »

John Cook explains at Skeptical Science:

Here at Skeptical Science, I tend to go on a bit about CO2. However, as readers often point out, CO2 is not the only driver of climate. There are a myriad of other radiative forcings that affect the planet’s energy imbalance. Volcanoes, solar variations, clouds, methane, aerosols – these all change the way energy enters and/or leaves our climate. So why the focus on CO2? Is it because I’m a hysterical treehugger determined to run peoples’ lives with a one world government? Or is there a rational, scientific reason for this CO2 preoccupation? Let’s find out which…

When I first started investigating global warming science, I attempted to discern the cause by a process of elimination. I studied all possible causes and ruled out any that couldn’t be causing all the warming. As my understanding grew, I came to realise this was an inappropriate approach. Understanding what drives climate does not occur by a process of elimination. It’s happens by a process of integration. There are many influences of climate and they all need to be considered together to gain the full picture.

For clarity, let me note a few definitions. Radiative forcing is loosely defined as the change in net energy flow at the top of the atmosphere. In this post, we’re talking about the radiative forcing from 1750 to 2005. Values are taken from Chapter 2 of the IPCC AR4 which in turn took all their values from peer reviewed papers – apologies that I was too lazy to cite all the original sources. Positive radiative forcing has a warming effect (so obviously, negative radiative forcing has a cooling effect)…

Continue reading.

Written by LeisureGuy

24 October 2009 at 10:12 am

CO2 was higher in Earth’s past

with 2 comments

This post explains and accounts for global warming in historical times—since 1850, roughly—based solely on CO2 buildup in the atmosphere from human activity. Indeed, we now have actual measurements of the heat trapped by greenhouse gases, and human-created CO2 is clearly the culprit, based on direct observations. But one final objection has been raised: if CO2 in the atmosphere traps heat, then high CO2 levels should create high global temperatures—so how does one explain this graph (click graph to enlarge):

paleocarbon

I actually don’t know enough to explain it myself, so I’ve asked for help. John Cook of Skeptical Science says that he plans to write a post dealing directly with that graph, but did point me to two posts that help explain what happened.

First is this post in Skeptical Science:

The skeptic argument…

“The killer proof that CO2 does not drive climate is to be found during the Ordovician- Silurian (450-420 Ma) and the Jurassic-Cretaceous periods (151-132 Ma), when CO2 levels were greater than 4000 ppmv (parts per million by volume) and about 2000 ppmv respectively. If the IPCC theory is correct there should have been runaway greenhouse induced global warming during these periods, but instead there was glaciation.”
(source: The Lavoisier Group)

What the science says…

At the time of the Ordovician, the Earth’s climate was very different. Solar output was 4-5% lower than present day levels. Rather than separate continents, the single landmass of Gondwanaland, moving southward into higher southern latitudes, allowed ice sheets to grow.

With less heat from the Sun, there was less heat to trap—and one single landmass on earth, located near the South Pole, would have created a unique climate, unlike that of today.

Next, with more detail, this post from Scholars and Rogues contains a whole list of skeptic arguments with responses. Specifically, take a look at:

Myth #6: CO2 concentrations are not correlated with global temperature due to periods in the geologic history when CO2 was higher and the planet was in an ice age.

The answer:

450 million years ago was the coldest in 0.5 billion years and also had the highest CO2 concentrations. Because of this, CO2 is not actually correlated global temperature (Source: distillation of multiple people’s claims at Wikipedia.org).

Debunking: Scientists aren’t sure what happened in the late Ordovecian period, when the world plunged into an ice age while CO2 levels were still very high (8-20x current levels). There are some ideas about what happened, however. A 1995 paper titled Reconciling Late Ordovician (440 Ma) glaciation with very high (14X) CO2 levels suggests that the physical location of the megacontinent Gondwanaland may have had something to do with it, and later papers suggest that the problem could be one of resolution of the data – if we can’t tell what the CO2 levels were at the moment of glaciation, then we can’t say whether CO2 being removed from the atmosphere was the cause or not. And if the high CO2 levels plunged due to geologic processes (namely the rise of the Appalachian Mountains and a subsequent carbon sequestration due to the weathering of the mountains), then there would be a mechanism to explain how the CO2 was high while the temperature was also high – the data isn’t detailed enough to know better, so it was actually a lot lower than 8x-20x present day when Gondwanaland froze up. In fact, this identical process is proposed as the cause for the most recent spate of ice ages, with the Himalaya Mountains being the cause. However, ultimately we just don’t know enough about this particular instance to say for sure.

Ancient data

However, the correlation of CO2 and global temperature is well established over the last 650,000 years using ice core data. The image (click for a larger version) is a composite created by the IPCC from multiple different sources for the WG1 AR4 chapter 6 on Paleoclimate, Figure 6.3, page 444. The black line shows a proxy for local temperature (deuterium), the green line is nitrous oxide, the red line is CO2, the blue line is methane, and the gray line is a proxy for land ice (low=more glaciers/larger ice caps). Notice that not only is CO2 concentration correlated with temperature, but so is methane concentration.But the most interesting part of this graph is the three stars in the upper right corner of the image. They are to scale with the associated lines and represent the 2000 concentrations of nitrous oxide (green star), CO2 (red star), and methane (blue star).

Written by LeisureGuy

18 October 2009 at 7:09 am

How do we know CO2 is causing warming?

with 9 comments

This post is especially for conservative09, who finds it difficult to believe that a seemingly small change in CO2 levels in the atmosphere (from 280 ppm in pre-industrial history to 387 ppm today—the highest level in 15 million years, a jump of 38%) could cause global warming. John Cook, in Skeptical Science:

We’ve just perused the empirical evidence that humans are raising atmospheric CO2 levels. In earlier posts, we noted that tallying up the planet’s heat content shows that our climate is accumulating heat, proof of global warming. But is there any evidence that links the two? Is there empirical data proving that increased CO2 contributes to the energy imbalance that causes global warming?

The greenhouse gas qualities of CO2 have been known for over a century. In 1861, John Tyndal published laboratory results identifying CO2 as a greenhouse gas that absorbed heat rays (longwave radiation). Since then, the absorptive qualities of CO2 have been more precisely measured and quantified by laboratory results and radiative physics theory (Herzberg 1953, Burch 1962, Burch 1970, etc).

Satellite measurements of the change in outgoing longwave radiation

So according to lab results and radiative physics, we expect that increasing atmospheric CO2 should absorb more longwave radiation as it escapes back out to space. Has this effect been observed? The paper Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997 (Harries 2001) attempts to find out. In 1970, NASA launched the IRIS satellite that measured infrared spectra between 400 cm-1 to 1600 cm-1. In 1996, the Japanese Space Agency launched the IMG satellite which recorded similar observations. Harries 2001 compared both sets of data to discern any changes in outgoing radiation over the 26 year period. The resultant change in outgoing radiation was as follows:

harries_radiation
Figure 1: Change in spectrum from 1970 to 1996 due to trace gases. ‘Brightness temperature’ indicates equivalent blackbody temperature (Harries 2001).

What they found was a drop in outgoing radiation at the wavelength bands that greenhouse gases such as CO2 and methane (CH4) absorb energy. The change in outgoing radiation over CO2 bands was consistent with theoretical expectations. Thus the paper found "direct experimental evidence for a significant increase in the Earth’s greenhouse effect".

This result has been confirmed by subsequent papers using the latest satellite data. Griggs 2004 compares the 1970 and 1997 spectra with additional satellite data from the NASA AIRS satellite launched in 2003. Chen 2007 extends this analysis to 2006 using data from the AURA satellite launched in 2004. Both papers found the observed differences in CO2 bands matched the expected changes based on rising CO2 levels. Thus we have empirical evidence that increased CO2 is preventing longwave radiation from escaping out to space.

Measurements of downward longwave radiation

What happens to longwave radiation that gets absorbed by greenhouse gases? The energy heats the atmosphere which in turn re-radiates longwave radiation. This re-radiated energy goes in all directions. Some of it makes its way back to the surface of the earth. Hence we expect to find increasing downward longwave radiation as CO2 levels increase.

Philipona 2004 finds that this is indeed the case – that downward longwave radiation is increasing due to an enhanced greenhouse effect. Evans 2006 takes this analysis further. By analysing high resolution spectral data, the increase in downward radiation can be quantitatively attributed to each of several anthropogenic gases. The results lead the authors to conclude that "these experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming."

So we have multiple lines of empirical evidence for CO2 warming. Lab tests show CO2 absorbing longwave radiation. Satellite measurements confirm that less longwave radiation is escaping to space. Surface measurements detect increased longwave radiation returning back to Earth at wavelengths matching increased CO2 warming. And of course the result of this energy imbalance is the accumulation of heat over the last 40 years.

And, if you’re still not convinced, you need to explain why: the empirical evidence supports the hypothesis that global warming is due to anthrogenic causes. See also:

  • Empirical evidence that humans are causing global warming
  • Comparing CO2 emissions to CO2 levels
  • How do we know CO2 is causing warming?
  • Are humans too insignificant to affect global climate?
  • How we know global warming is happening, Part 2
  • How we know global warming is still happening
  • Written by LeisureGuy

    15 October 2009 at 11:15 am

    Atmospheric CO2 levels

    leave a comment »

    David Adam writes in the Guardian in May 2008:

    The concentration of carbon dioxide in the atmosphere has reached a record high, according to new figures that renew fears that climate change could begin to slide out of control.

    Scientists at the Mauna Loa observatory in Hawaii say that CO2 levels in the atmosphere now stand at 387 parts per million (ppm), up almost 40% since the industrial revolution and the highest for at least the last 650,000 years.

    The figures, published by the US National Oceanic and Atmospheric Administration (NOAA) on its website, also confirm that carbon dioxide, the chief greenhouse gas, is accumulating in the atmosphere faster than expected. The annual mean growth rate for 2007 was 2.14ppm – the fourth year in the past six to see an annual rise greater than 2ppm. From 1970 to 2000, the concentration rose by about 1.5ppm each year, but since 2000 the annual rise has leapt to an average 2.1ppm.

    Scientists say the shift could indicate that the Earth is losing its natural ability to soak up billions of tons of carbon each year. Climate models assume that about half our future emissions will be re-absorbed by forests and oceans, but the new figures confirm this may be too optimistic. If more of our carbon pollution stays in the atmosphere, it means emissions will have to be cut by more than currently projected to prevent dangerous levels of global warming.

    Martin Parry, co-chair of the Intergovernmental Panel on Climate Change‘s working group on impacts, said: "Despite all the talk, the situation is getting worse. Levels of greenhouse gases continue to rise in the atmosphere and the rate of that rise is accelerating. We are already seeing the impacts of climate change and the scale of those impacts will also accelerate, until we decide to do something about it."

    Written by LeisureGuy

    15 October 2009 at 11:04 am

    How do we know CO2 is causing global warming

    leave a comment »

    The blog Skeptical Science: Examining the science of global warming skepticism should be on the radar of all global warming skeptics: only here are their arguments taken seriously, examined, and (alas) found wanting. Here’s a recent post:

    We’ve just perused the empirical evidence that humans are raising atmospheric CO2 levels. In earlier posts, we noted that tallying up the planet’s heat content shows that our climate is accumulating heat, proof of global warming. But is there any evidence that links the two? Is there empirical data proving that increased CO2 contributes to the energy imbalance that causes global warming?

    The greenhouse gas qualities of CO2 have been known for over a century. In 1861, John Tyndal published laboratory results identifying CO2 as a greenhouse gas that absorbed heat rays (longwave radiation). Since then, the absorptive qualities of CO2 have been more precisely measured and quantified by laboratory results and radiative physics theory (Herzberg 1953, Burch 1962, Burch 1970, etc).

    Satellite measurements of the change in outgoing longwave radiation

    So according to lab results and radiative physics, we expect that increasing atmospheric CO2 should absorb more longwave radiation as it escapes back out to space. Has this effect been observed? The paper Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997 (Harries 2001) attempts to find out. In 1970, NASA launched the IRIS satellite that measured infrared spectra between 400 cm-1 to 1600 cm-1. In 1996, the Japanese Space Agency launched the IMG satellite which recorded similar observations. Harries 2001 compared both sets of data to discern any changes in outgoing radiation over the 26 year period. The resultant change in outgoing radiation was as follows:

    harries_radiation
    Figure 1: Change in spectrum from 1970 to 1996 due to trace gases. ‘Brightness temperature’ indicates equivalent blackbody temperature (Harries 2001).

    What they found was a drop in outgoing radiation at the wavelength bands that greenhouse gases such as CO2 and methane (CH4) absorb energy. The change in outgoing radiation over CO2 bands was consistent with theoretical expectations. Thus the paper found “direct experimental evidence for a significant increase in the Earth’s greenhouse effect”.

    This result has been confirmed by subsequent papers using the latest satellite data. Griggs 2004 compares the 1970 and 1997 spectra with additional satellite data from the NASA AIRS satellite launched in 2003. Chen 2007 extends this analysis to 2006 using data from the AURA satellite launched in 2004. Both papers found the observed differences in CO2 bands matched the expected changes based on rising CO2 levels. Thus we have empirical evidence that increased CO2 is preventing longwave radiation from escaping out to space.

    Measurements of downward longwave radiation

    What happens to longwave radiation that gets absorbed by greenhouse gases? The energy heats the atmosphere which in turn re-radiates longwave radiation. This re-radiated energy goes in all directions. Some of it makes its way back to the surface of the earth. Hence we expect to find increasing downward longwave radiation as CO2 levels increase.

    Philipona 2004 finds that this is indeed the case – that downward longwave radiation is increasing due to an enhanced greenhouse effect. Evans 2006 takes this analysis further. By analysing high resolution spectral data, the increase in downward radiation can be quantitatively attributed to each of several anthropogenic gases. The results lead the authors to conclude that “this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming.”

    So we have multiple lines of empirical evidence for CO2 warming. Lab tests show CO2 absorbing longwave radiation. Satellite measurements confirm that less longwave radiation is escaping to space. Surface measurements detect increased longwave radiation returning back to Earth at wavelengths matching increased CO2 warming. And of course the result of this energy imbalance is the accumulation of heat over the last 40 years.

    Acknowledgements: A big thanks must go to AGW Observer. Their lists of papers on changes in outgoing longwave radiation, changes in downward longwave radiation and laboratory measurements of CO2 absorption properties made this post possible.

    Written by LeisureGuy

    12 October 2009 at 12:33 pm

    <span>%d</span> bloggers like this: