The OCO-2, aka, Orbiting Carbon Observatory 2, is a satellite that measures CO2 in the atmosphere, using a spectrograph.
From a news article in today’s Science, “One of the crowning achievements of modern environmental science is the Keeling curve, the detailed time series of the concentration of atmospheric carbon dioxide (CO2) begun in 1958 that has enabled deep insights into the mechanisms of global climate change. These measurements were difficult to make for most of their 60-year history, involving the physical collection of air samples in flasks at a small number of sites scattered strategically around the globe and the subsequent analysis of their CO2 inventories in a handful of laboratories throughout the world.”
The purpose of the OCO-2 was to make these measurements much more accurate and efficient, and to provide more granularity in the details. The space craft was launched in July 2014, replacing an earlier OCO (OCO-1, if you like) which was launched in 2009.
Do not tell Donald Trump about this satellite. He’ll have it shot down.
First, there is the annual up and down cycle that happens because there is more land in the Northern Hemisphere. I won’t explain that to you now because I know you can figure out why that happens.
Second, there is natural variation up and down aside from that annual cycle that has to do with things like volcanoes and such. This includes the rate of forest fires, which increase greenhouse gases by turning some of the Carbon trapped in plant tissue into gas form as CO2. (That was a hint for the answer to the first reason!)
There was a big spike in CO2 concentration this year, and it was caused by El Nino increasing forest fire output, which in turn, freed up some of that CO2. Also, regional drought in some places simply slowed down plant growth, leaving some Carbon stranded in the atmosphere.
So was that natural? Not at all. ENSO cycles, that cause El Nino and La Nina constitute and oscillation in rainfall patterns, and part of that results in extra forest fires or other effects as mentioned. But these effects are caused directly by weather disruption. Human caused global warming was already doing that. The severe El Nino of 2014-2016 was more severe (and probably longer) than any, or almost any, ever observed, precisely because it was a big dermatological monster sitting on top of a big hill made by anthropogenic global warming.
But there is also another,subtler but very important lesson in this event. At any given time we could have what would normally be a “natural” shift to bad conditions. But under global warming, such a shift can be transformed from a disaster to a much bigger disaster. In this way, think of climate change as the steepening of the drop off alongside the road from a 2 foot ditch to a 10 foot embankment. When we drive off the road due to natural forces (some ice, for example) without global warming,we get bounced around a bit. With global warming we get to rely on our airbags to save us, but the airbag deployment will probably break both our arms and mess up our face.
Anyway, the confirmation of the role of El Nino comes from new research discussed here.
A paper just published in Nature reports on the direct measurement of the effects of human greenhouse gas pollution on the heating of the Earth’s atmosphere. This is empirical verification of anthropogenic global warming.
Since the Industrial Revolution, when humans started polluting the Earth’s atmosphere with copious amounts of long lived greenhouse gases released from entombment as fossil fuels, the amount of CO2 in the atmosphere has skyrocketed from close to 250 parts per million (ppm) to about 400ppm. In fact, February was the first month since records have been kept to average over 400ppm, though that value has been reached several times over the last year or so. This is the highest concentration of CO2 in the atmosphere in a very long time. Direct measurements of air trapped in glacial ice confirms that CO2 has been well below 300ppm for the last 800,000 years. We can’t measure CO2 as easily for periods before this, but it can be estimated, and the best estimates suggest that the last time our planet has had CO2 levels of 400ppm or more is during the very early Pleistocene or, more likely, the Late Pliocene, between roughly 2.5 and 3.5 million years ago.
The transition from higher CO2 levels, and a warmer Earth to a cooler Earth changed the planet’s ecology considerably, giving rise for the the first time to widespread grasslands (much of that now converted to vast farmlands), reduced forests, repeated glaciations and other changes. It is generally accepted that these changes directly or indirectly caused many of the key steps in human evolution. So, millions of years ago, the planet changed to one inhabited by our immediate ancestors and eventually our own species, and our physiology, culture, technology, psychology, and everything else evolved in this new context. Re-heating the Earth to Miocene levels in a very short period of time will have dramatic consequences and will possibly make it impossible for Humans to live as we do now on this planet.
The science behind this is somewhat complicated but the basics can be easily understood. The sun provides heat to the Earth, but if our atmosphere consisted only of non-greenhouse gases, much of that heat would immediately escape and our planet would be very cold. Adding greenhouse gasses to such a hypothetical Earth would cause a heat imbalance that would eventually increase the average temperature of the oceans, the air near the surface (where we live), the upper several meters of the Earth itself. This heat imbalance would also eventually melt persistent ice such as found today in the world’s glaciers, which in turn would cause a dramatic rise in sea level. Around the edges of the Earth’s continents are preserved ancient beaches or shorelines where the Miocene (or earlier) ocean once ended. Between these ancient shorelines and the modern shoreline, in most places, exist a very large percentage of the Earth’s human population and, in some areas, vast regions that are farmed to produce the world’s supply of food.
We know how this works mainly from two different sources of information. First, there is the basic physics, backed up by laboratory experiments, showing that added greenhouse gasses provide the heat imbalance that causes what we call global warming. Second, we have been measuring the surface temperature of the Earth for many decades, and we can see the heating. One of the most important things to know about this is that the current level of heating is not that expected for the current level of CO2. The current concentration of CO2 and other greenhouse gases should produce much more heating but it takes time, in the order of decades, for the imbalance to even out. In other words, the increase in greenhouse gases caused by human pollution so far is expected to produce continued warming for decades to come. The primary driver, CO2, is not expected to leave the atmosphere for centuries. So, we are currently locked in to a significant rise in heat, and as we continue to add more CO2 to the atmosphere, the total effect will increase.
In between these two basic facts — the physics of greenhouse pollution and the observation of the effects of greenhouse pollution — is the direct observation of what scientists call “radiative forcing.” Radiative forcing is the degree of perturbation of the planet’s heat energy balance caused by these changes in the atmosphere. To measure radiative forcing, one would observe the energy provided to a given location by the sun, and observe the heat leaving the planet, at two different time periods with different concentrations of greenhouse pollution.
This has been done only a few times, using a range of different technologies. In 2001 scientists reported satellite-observed changes in greenhouse pollution forcing between 1970 and 1997, providing “… direct experimental evidence for a significant increase in the Earth’s greenhouse effect that is consistent with concerns over radiative forcing of climate.” This study was replicated and extended in 2013. In 2004 researchers published a paper that reported measurements at eight meteorological stations in Europe, at various elevations and locations. They measured energy flux that they could attribute to a combination of increased vapor (a greenhouse gas naturally present but enhanced by added CO2) and CO2 over eight years. “… after subtracting for two thirds of temperature and humidity rises, the increase of cloud-free longwave downward radiation (+1.8(0.8) Wm?2) remains statistically significant and demonstrates radiative forcing due to an enhanced greenhouse effect.” The science of directly measuring the “smoking gun” of greenhouse gas pollution is further discussed here: Empirical evidence that humans are causing global warming
The current study, Observational determination of surface radiative forcing by CO2 from 2000 to 2010 by D. R. Feldman, W. D. Collins, P. J. Gero, M. S. Torn, E. J. Mlawer and T. R. Shippert, takes a different approach than the earlier studies and in some ways is a more direct measurement. They used very precise spectroscopic instrumentation located at two sites, one in Oklahoma and one in Alaska, to measure what was happening with the Sun’s energy. They also measured variables that influence the behavior of the energy, such as ambient temperature, water vapor, and clouds. After factoring out everything but the CO2, they were able to accurately measure the effects of radiative forcing. The study was carried out from 2000 to 2010, during which time the atmospheric concentration of CO2 rose 22ppm. From the paper, these “…results confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions, and provide empirical evidence of how rising CO2 levels, mediated by temporal variations due to photosynthesis and respiration, are affecting the surface energy balance.”
So, what’s new? In a way, nothing. This is one of those scientific findings that could easily result in a “well, duh” response. We already knew the basic physics, and we already observed the global warming that results from human greenhouse gas pollution. However, it is important and appropriate to directly measure and describe processes that underly such an important phenomenon. Daniel Feldman, lead author, told me, “CO2 concentrations have been measured at several surface stations for decades, including the prominent Keeling curve. The actual radiative forcing (like in IPCC AR5 WG1 Chapter 8), which is distinct from surface temperature, is based, for the most part, on calculations which are informed by laboratory measurements and quantum mechanics. In 2001, John Harries et al published a paper in Nature in which they inferred the greenhouse effect at the TOA based on differencing two satellite instrument data records, but our study is the first to see the effect at the surface from observations.”
The two very far apart sites were chosen to allow comparison of two very different areas of the Earth. I wondered if the CO2 concentrations were different in the two areas (they should be the same, but worth asking just in case!) and if the basic nature of the forcing was similar. Feldman told me that the CO2 levels were not different, and that “we were not able to see a significant difference in the forcing per unit CO2 at the two sites.”
The researchers produced a video showing their results:
Caption from the press release: How carbon dioxide concentrations in the atmosphere have changed (blue line) and their warming effect (‘forcing’) on the climate over the same time period (orange line), for the southern Great Plains site (first graph shown) and the northern Alaska site (second). The seasonal fluctuations are caused by the rise and fall in plant photosynthesis in summer and winter, respectively. Source: Feldman et al. ( 2015)
After a five-year decrease in the amount of carbon dioxide pumped into the atmosphere from burning fossil fuels, U.S. greenhouse gas emissions are on the rise again. The culprit: a rebounding economy.
CO2 emissions from fossil fuels rose 2.39 percent in 2013 compared with 2012 and grew 7.45 percent for the first two months of 2014 compared with the same period in 2013, according to new data released by the U.S. Energy Information Administration (EIA). The jump puts an end to the annual decrease that had occurred from 2008 through 2012.
So be careful of that misleading graph, and keep working on reducing emission. This problem will not solve itself.