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Future Emissions Scenario Requirements Part II

Ask and ye shall receive.  I recently wrote about what future GHG emissions scenarios included in terms of emission reduction requirements.  I have maintained for some time now that most of the IPCC’s emission and concentration scenarios are essentially useless for practical planning purposes.  Sure, they’re interesting academically, but we climate scientists can’t just study something for the sake of studying it in today’s tight federal budget environment.

In that post, I showed some graphics from a 2013 Nature paper which combined historical emissions as well as projected emissions.  Due to the article’s age, I had to search for additional data which showed more recent emissions.  I also showed a simple calculation of projected emissions assuming constant 2.1% annual emissions growth and how different emissions growth would have to be in order to achieve an emissions scenario many scientists characterize as ‘doable’: RCP4.5.

Well, a new Nature Climate Change paper (26Feb2014) updates the 2013 graph I showed, with some small changes:

 photo CO2_Emissions_AR5_Obs_Nature_article_zps1e766d71.jpg
Figure 1. Historical (black dots) and projected CO2 emissions from a Nature Climate Change article (subs. req’d).  Bold colored lines (red (RCP8.5), yellow (RCP4.5), green (RCP6), and blue (RCP2.6)) represent IPCC AR5 RCP-related emission scenarios.

Note that this figure shows exactly what I wrote about in my earlier post: historical emissions are tracking at or above the RCP8.5 scenario.  They also exceed the other three scenarios so far in the early 21st century.  These differences are relatively small so far (they will grow with time), but the trend difference between historical and RCP2.6 is already important.  As the figure shows, if we wanted to match RCP2.6 (and keep 2100 global mean annual temperatures near 2C above pre-industrial), emissions would have to be declining for multiple years already.  They aren’t.  Our actual annual emissions already exceed the annual maximum assumed by RCP2.6.  If we were to match RCP2.6 at some time in the future, emission reductions would have to be larger than RCP2.6 assumes, which is currently technologically impossible.

The figure also shows that if we continue at or along the RCP8.5 pathway, we will exceed the 2°C policy target by approximately 2046.  The paper begins with this short and sweet abstract:

It is time to acknowledge that global average temperatures are likely to rise above the 2 °C policy target and consider how that deeply troubling prospect should affect priorities for communicating and managing the risks of a dangerously warming climate.

And it includes this well-written paragraph:

This global temperature target has brought a valuable focus to international climate negotiations, motivating commitment to emissions reductions from several nations. But a policy narrative that continues to frame this target as the sole metric of success or failure to constrain climate change risk is now itself becoming dangerous, because it ill-prepares society to confront and manage the risks of a world that is increasingly likely to experience warming well in excess of 2°C this century.

I wouldn’t have used the term `dangerous` because it conveys a judgmental aspect to an objective statement.  But that’s personal style.  I agree completely with the underlying message.  If we have a small (I would say nearly zero) chance of keeping warming below 2°C this century, then 2°C shouldn’t be the target.  We can make an infinite number of possible targets, but most of them will be unachievable.  How much effort should we put into such targets?  How supportive of additional climate policies will the public be if initial targets fail early?  These aren’t simply academic questions.  Many climate activists think they’re convinced of how important action is, but their rhetoric doesn’t support that conviction.  They’re more ideological than they’d care to admit.

I met someone at a talk at the University of Colorado on Monday and ended up having lunch with them to exchange economic information for climate information.  I tried to convince them of the need to switch targets now, to no avail.  I ran into a basic problem of climate communication.  This person has a worldview and I was in the unenviable position of trying to modify that worldview.  Just as many climate communicators try to do with climate skeptics.  It’s incredibly difficult to do this because you’re dealing with a lifetime of information and experience overlaying a biology that is predisposed to that very worldview.

I will continue to post about historical versus projected emission/concentration pathways.  If activists really are supportive of the objective science as they claim, I think they will eventually shift their target.  They will of course have to come to terms with what they will initially perceive as a failure.  But the faster they can do that, the sooner we can set more reasonable and achievable targets and start making headway towards mitigation.


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Future Emissions Scenario Requirements & Arctic Warming [With Update]

A recent research article didn’t generate anything terribly earth-shattering, but I wanted to write about some writing on it because it deals with a recurring theme on this blog.  For context, I’ll start with the news release and article (article subs. req’d).  In a nutshell,

Climate model projections show an Arctic-wide end-of-century temperature increase of +13∘ Celsius in late fall and +5∘ Celsius in late spring if the status quo continues and current emissions increase without a mitigation scenario. In contrast, the mean temperature projection would be +7∘ Celsius in late fall and +3∘ Celsius in late spring by the end of the century if a mitigation scenario to reduce emissions is followed, concludes the paper titled, “Future Arctic Climate Changes: Adaptation and Mitigation Timescales.”

Again, there is nothing terribly shocking there.  If we do nothing, the Arctic will likely warm a whole lot more than if we implement mitigation policies.

But that paragraph could use some additional context.  What do the greenhouse gas emissions scenarios look like to generate those varying warming projections?  To get a little technical (stay with me), the authors compared two out of four of the Intergovernmental Panel on Climate Change’s (IPCC) Representative Concentration Pathways (RCPs): RCP8.5 and RCP4.5.  These pathways represent an additional 8.5 W/m^2 and +4.5 W/m^2 radiative forcing at the year 2100 relative to pre-industrial values.

But even though I’ve taken a graduate level radiation course and I’m using these same pathways in my own research, I don’t really know what +8.5 W/m^2 radiative forcing is, and neither do most people.  It’s a number with units that is not intuitively obvious.  This is where climate scientists underperform in communicating with the public and where I come in.

So instead of losing ourselves in the technical details, how can we understand what these two pathways represent?  Qualitatively, RCP8.5 represents a scenario in which we do not enact GHG mitigation policies until after the year 2100.  Economic growth and GHG emissions continue to grow throughout the rest of this century due to 4x 2000′s global energy use.  The radiative forcing is induced by 1370 ppm CO2-eq (CO2 and other GHGs).

By comparison, RCP4.5 represents a scenario that stabilizes forcing at 4.5 W/m^2 without overshooting it and has 650 ppm CO2-eq by 2100 (583 ppm CO2; 2013 mean CO2 concentration: 397 ppm).  Global energy use is just over 2x 2000 levels.  RCP4.5 achieves relatively lower CO2 concentrations by steadily decreasing the amount of carbon per energy unit supplied from 2000 to 2050, then decreasing the carbon/energy ratio very rapidly between 2050 and 2075, then leveling off from 2075-2100.  It does this via wider renewable energy deployment, but predominantly fossil fuel use with carbon capture and sequestration deployment.

In other words, RCP4.5 chiefly relies on slower CO2 concentration growth by assuming widespread and rapid deployment of technologies that do not exist today.  This point is very important to understand.

In a write-up on this same research, Joe Romm concludes thusly (emphasis mine):

This study essentially writes off the possibility of humanity doing any better:

The RCP2.6 scenario requires a 70% reduction of emissions relative to present levels by 2050, a scenario that is highly unlikely in view of the current trajectory of emissions and the absence of progress toward mitigation measures. We refer to the RCP8.5 and RCP4.5 future scenarios as business-as-usual and mitigation.

But the fact is that RCP2.6 — which is about 421 ppm CO2 — is entirely feasible from both a technical and economic perspective. It is only the irrationality, myopia, and, it would seem, self-destructiveness of Homo sapiens that make it “highly unlikely.”

No, it’s not.  RCP2.6 makes many more assumptions about technological capabilities and deployment than does RCP4.5.  It does this more quickly than RCP4.5 by modeling declining carbon per energy unit between 2010 and 2025 (which hasn’t happened yet), then declining much more rapidly starting in 2025 (only 10 years away) until 2050, then slowing down in 2050 and again in 2075.  But here is the kicker: it assumes negative carbon per energy unit after 2075!  How does it do this?  By assuming more carbon will be removed from the atmosphere than emitted into it starting in 2075 and continuing thereafter.  Do we have carbon capture and sequestration (CCS) technologies ready for rapid global deployment?  No, there is to my knowledge only a couple of utility-scale projects currently operating and they haven’t achieved the level of capture and sequestration this pathway assumes.

In order for CCS to operate at the level RCP2.6 assumes, global investment in the technology would have to increase by many factors for years.  Is there any discussion of this occurring in any government?  Will we price carbon-based fuels without interference (i.e., an end to market manipulation by fossil fuel entities and governments)?  No and these things aren’t likely to begin any time soon.

Simply put, RCP2.6 is a fantasy scenario [see update below].  Absent global economic collapse that dwarfs the Great Depression, CO2 emissions and concentrations will continue to increase as economies continue to rely on relatively cheap dirty fossil fuels with manipulated prices.  At this point, I think RCP4.5 is to a lesser extent another fantasy scenario.  That’s neither irrational nor myopic, but realistic based on historical climate policy and my own reading of where international climate policy is likely to exist in the next 35 years.  We are currently on the RCP8.5 pathway.  Researchers use RCP4.5 because it is illustratively different from RCP8.5.  They think it is technically feasible simply because they understand the likely science ramifications of RCP8.5 and misunderstand the public’s desire for continued increasing quality of life that comes with fossil fuel use.  Case in point: researchers have shown the difference between “worst-case” and “best-case” climate scenarios for 30+ years.  Nobody enacted robust climate policy in response to these comparisons.  To continue to do so moving forward is a waste of resources.

[Update]

I wanted to share some updated data demonstrating my statement that RCP2.6 and RCP4.5 are “fantasy scenarios”.  Here are two plots I used in a related post in last 2012:

 photo CO2EmissionsScenarios-hist-and-RCP-2012-b.png

Figure 1. Historical (black dots) and projected (out to 2050 only) CO2 emissions from a Nature Climate Change article (subs. req’d).  Bold colored lines (red, yellow, gray, and blue) represent IPCC AR5 RCP-related emission scenarios.   Thick green dashed lines and thin green solid lines represent SRES emission scenarios used in IPCC AR4.  Light blue dashed lines represent IS92 scenarios.  Different generation scenarios are presented together for inter-report comparison purposes.

 photo CO2EmissionsScenarios-hist-and-RCP-2012.png

Figure 2. As in Figure 1 except projections shown to year 2100 and RCP scenarios highlighted.

Figures 1 and 2 show historical and projected annual CO2 emissions in Pg/year from 1980 until 2050 and 2100, respectively.  Historical data end in 2011 because the paper was published in 2012.  So there are two more year’s data available to us now.  How do you think global CO2 emissions changed since 2011?  Did they decrease, stay the same, or increase?

It’s more challenging than it should be to find similar graphics, but I found this update:

 photo CO2_emissions_Global_Carbon_Project_2013_zps7214b665.jpg

Figure 3. Historical (1990-2012; 2013 projection) global CO2 emissions in GtC/year (1 PgC = 1 GtC).

As Figure 3 shows, global CO2 emissions rose in 2012 compared to 2011, and emissions likely rose further in 2013 compared to 2012.  It further shows that emission rates increased only by 1.0%/year in the 1990s and accelerated to 2.7%/year in the 2000s.  While recent year-0ver-year increases aren’t at 2000 mean levels, they are at least twice that of 1990 levels.  In other words, there has been no stabilization of CO2 emissions, let alone a decrease, as RCP2.6 and RCP4.5 assume.

A fair counterpoint can be made that RCP2.6 assumes a decline starting in 2020, while RCP4.5′s decline starts in 2040.  Sure enough, Figure 1 and 2 demonstrate those assumptions.  To that, I say Figure 1 and 2 also shows RCP2.6′s maximum annual emissions peak at 2010 levels.  Emissions have already increased at 2%+/year since then historically.  For argument sake, let’s say emissions will peak in 2020.  Historical emissions will then be higher than RCP2.6 assumed, which would require even more CO2 removal to achieve <2C stabilization by 2100.  More CO2 removal means more efficient and widespread deployment than RCP2.6 already assumes, which makes it less likely to occur.

RCP4.5 assumes peak annual emissions in 2040 of approximately 11 PgC/year.  If annual growth rates continue near 2.1%, we’ll actually reach that level in 2018 – 22 years ahead of RCP4.5′s assumption.  What emissions growth rate is required to hit 11 PgC/year in 2040?  See the chart below:

 photo CO2Emissions-21and0475_growth_rates_zps20b1f74a.png

Figure 4. Historical (1959-2012) and projected (2013-2040) global annual CO2 emissions using mean 2000′s emissions growth (blue) and calculated emissions required to achieve 11 GtC/year in 2040 (red).  [Historical data: 2013 Global Carbon Project.]

Note that the RCP4.5 scenario has declining emissions growth rate between 2030 and 2040 while my computations uses constant growth rate assumption.  Still, this calculation sheds some light on required changes to achieve RCP4.5 scenario assumptions.  Figure 4 shows that if future emissions grow at constant rate of 2.1%/year (less than the mean 2000′s rate; more than the mean 1990′s rate), 2040 emissions will total >17 GtC/year (remember RCP4.5′s maximum of 11 GtC/year could be achieved as early as 2018).  To max out at 11 GtC/year, emissions would either have to grow at no more than 0.475%/year – less than half the 1990′s mean value – or grow more quickly in the near future, stabilize quickly, and decrease every year following 2030.

RCP2.6 and RCP4.5 demand that countries begin to change their entire energy production fleet from fossil fuels to renewables – either immediately (RCP2.6) or within the next 10-15 years (RCP4.5).  What costs are associated with this conversion?  How many people without energy access today are denied energy access in the future?  That is something that Romm doesn’t address in his talking point that “the fact is that RCP2.6 — which is about 421 ppm CO2 — is entirely feasible from both a technical and economic perspective.”  421 ppm CO2 means no higher concentration than what will occur by 2025.

A permanent emissions decline has obviously never happened historically.  What basis allows for the assumption that it will occur starting in 2030?  More sweeping and effective policies than have ever been implemented are required.  The point to this exercise is to demonstrate that we can play games with numbers all day, but the real world is quite different from economic and climate models as well as Excel spreadsheets.  Unless and until we see real world evidence that emissions stabilization occurs, I see little reason to discuss what RCP2.6 or RCP4.5 shows beyond what “could be” as a rhetorical exercise.


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Energy Generation Now & in the Future

I finished my last post with an important piece of data.  Out of 100 quads of energy the US generates every year, the vast majority of it (83%) comes from fossil fuel sources – sources that emit greenhouse gases when we burn them.  The same is true for the vast majority of other countries, and therefore for the global portfolio as well.  Here is a graphic showing global energy consumption distribution by fuel type from 1990 through 2010 and into the future:

 photo EIA-WorldEnergyConsumptionbyfueltype1990-2040_zps8d8ae886.png

Figure 1. Global fuel-type energy consumption, 1990-2040 (EIA 2013 Energy Outlook).

The global picture is somewhat different from the US picture: liquids’ energy (e.g., oil) exceed coal energy, which exceed natural gas.  All three of these carbon-intensive energy sources, which power our developed, high-wealth lifestyles, greatly exceed renewables (which hydropower dominates), which exceeds nuclear.  It is these type of energy forecasts that lead to the suite of IPCC emissions pathways:

 photo IPCCAR5RCPScenarios_zps69b8b0d5.png

Figure 2. IPCC Fifth Assessment Report Representative Concentration Pathway (RCP) CO2-eq concentrations.

Note that our current emissions trajectory more closely resembles the RCP8.5 pathway (red) than the other pathways.  This trajectory could lead to a 1000+ ppm CO2-eq concentration by 2100, or 2.5X today’s concentration value.  Stabilizing global temperature increases at less than 2C by 2100 requires stabilizing CO2-eq concentrations below 450 and quickly decreasing, which is best represented by the RCP2.6 pathway above (green).  This pathway is technologically impossible to achieve as of today.  The only way to make it possible is to invest in innovation: research, development, and global deployment of low-carbon technologies.  We are not currently doing that investment; nor does it look likely we will in the near future.

Let’s take a further look at the recent past before we delve further into the future.  Environmental and renewable energy advocacy groups tout recent gains in renewable energy deployment.  We should quietly cheer such gains because they are real.  But they are also miniscule – far too little deployment at a time when we need exclusive and much wider deployment of renewable energy globally to shift our emissions pathway from RCP8.5 to RCP2.6.  Here is a graphic showing global use of coal in the past 10+ years:

 photo WorldCoalConsumption-2001-2011_zps68aea439.jpg

Figure 3. Global coal use in million tonnes of oil-equivalent 2001-2011 (Grist).

Climate and clean energy advocates like to report their gains in percentage terms.  This is one way of looking at the data, but it’s not the only way.  For instance, coal usage increased by 56% from 2001 to 2011.  This is a smaller percentage than most renewable energy percentage gains in the same time period, but the context of those percentages is important.  As you’ll see below, renewable energy gains really aren’t gains in the global portfolio.  The above graph is another way to see this: if renewable energy gains were large enough, they would replace coal and other fossil fuels.  That’s the whole point of renewable energy and stabilizing carbon emissions, right?  If there is more renewable energy usage but also more coal usage, we won’t stabilize emissions.  Here is another way of looking at this statement:

 photo GlobalEnergyConsumption-Carbon-FreeSources1965-2012_zps1a06c9a0.png

Figure 4. Global Energy Consumption from Carbon-Free Sources 1965-2012 (Breakthrough).

Carbon-free energy as a part of the total global energy portfolio increased from 6% in 1965 to 13% in the late 1990s.  This is an increase of 200% – which is impressive.  What happened since the 1990s though?  The proportion was actually smaller in 2011 than it was in 1995 in absolute terms.  At best, carbon-free energy proportions stagnated since the 1990s.  Countries deployed more carbon-free energy in that time period, but not enough to increase their proportion because so much new carbon energy was also deployed.  What happened starting in the 1990s?  The rapid industrialization of China and India, predominantly.  Are developing countries going to stop industrializing?  Absolutely not, as Figure 1 showed.  It showed that while renewable energy consumption will increase in the next 30 years, it will likely do so at the same rate that natural gas and liquids will.  The EIA projects that the rate of increase of coal energy consumption might level off in 30 years, after we release many additional gigatonnes of CO2 into the atmosphere, ensuring that we do no stabilize at 450 ppm or 2°C.

Here is the EIA’s projection for China’s and India’s energy consumption in quads, compared to the US through 2040:

 photo EIA-EnergyConsumption-US-CH-IN1990-2040_zps70837e84.png

Figure 5. US, Chinese, and Indian energy consumption (quads) 1990-2040 (EIA 2013 Energy Outlook).

You can see the US’s projected energy consumption remains near 100 quads through 2040.  China’s consumption exceeded the US’s in 2009 and will hit 200 quads (2 US’s!) by 2030 before potentially leveling off near 220 quads by 2040.  India’s consumption was 1/4 the US’s in 2020 (25 quads), and will likely double by 2040.  Where will an additional 1.5 US’s worth of energy come from in the next 30 years?  Figure 1 gave us this answer: mostly fossil fuels.  If that’s true, there is no feasible way to stabilize CO2 concentrations at 450 ppm or global mean temperatures at 2°C.  That’s not just my opinion; take a look at a set of projections for yourself.

Here is one look at the future energy source by type:

 photo GlobalEnergyByType-2013ProjectionbyBNEF_zps36f9806f.jpg

Figure 6. Historical and Future Energy Source by Type (BNEF).

This projection looks rosy doesn’t it?  Within 10 years, most new energy will come from wind, followed by solar thermal.  But look at the fossil fuels!  They’re on the way out.  The potential for reduced additional fossil fuel generation is good news.  My contention is that it isn’t happening fast enough.  Instead of just new energy, let’s look at the cumulative energy portfolio picture:

 photo GlobalEnergyTotalByType-2013ProjectionbyBNEF_zps88331d51.jpg

Figure 7. Historical and Future Total Energy Source by Type (BNEF).

This allows us to see how much renewable energy penetration is possible through 2030.  The answer: not a lot, and certainly not enough.  2,000 GW of coal (>20% of total) remains likely by 2030 – the same time when energy experts say that fossil fuel use must be zero if CO2 concentrations are to remain below 450 ppm by 2100.  But coal isn’t the only fossil fuel and the addition of gas (another 1,700 GW) and oil (another 300 GW) demonstrates just how massive the problem we face really is.  By 2030, fossil fuels as a percentage of the total energy portfolio may no longer increase.  The problem is the percentages need to decrease rapidly towards zero.  Nowhere on this graph, or the next one, is this evident.  The second, and probably more important thing, about this graph to note is this: total energy increases at an increasing rate through 2030 as developing countries … develop.

 photo EIA-WorldEnergyConsumptionbyfueltype1990-2040_zps8d8ae886.png

Figure 8. Global fuel-type energy consumption, 1990-2040 (EIA 2013 Energy Outlook).

The EIA analysis agrees with the BNEF analysis: renewables increase through 2030.  The EIA’s projection extends through 2040 where the message is the same: renewables increase, but so do fossil fuels.  The only fossil fuel that might stop increasing is the most carbon intensive – coal – and that is of course a good thing.  But look at the absolute magnitudes: there could be twice as many coal quads in 2040 as there were in 2000 (50% more than 2010).  There could also be 50% more natural gas and 30% more liquid fuels.  But the message remains: usage of fossil fuels will likely not decline in the next 30 years.  What does that mean for CO2 emissions?

 photo EIA-WorldEnergy-RelatedCO2Emissionsbyfueltype1990-2040_zps417bffc4.png

Figure 9. Historical and projected global carbon dioxide emissions: 1990-2040 (EIA 2013 Energy Outlook).

Instead of 14 Gt/year (14 billion tonnes per year) in 2010, coal in 2040 will emit 25 Gt/year – almost a doubling.  CO2 emissions from natural gas and liquids will also increase – leading to a total of 45 GT/year instead of 30 GT/year.  The International Energy Agency (IEA) estimated in 2011 that “if the world is to escape the most damaging effects of global warming, annual energy-related emissions should be no more than 32Gt by 2020.”  The IEA 2012 World Energy Outlook Report found that annual carbon dioxide emissions from fossil fuels rose 1.4 percent in 2012 to 31.6 Gt.  While that was the lowest yearly increase in four years, another similar rise pushes annual emissions over 32Gt in 2014 – six years ahead of the IEA’s estimate.  Based on the similarity between our historical emissions pathway and the high-end of the IPCC’s AR4 SRES scenarios (see figure below), 2°C is no longer a viable stabilization target.

 photo CO2_Emissions_IPCC_Obs_2012_zpsd3f8cb8f.jpg

Figure 10. IEA historical annual CO2 emissions and IPCC AR4 emissions scenarios: 1990-2012 (Skeptical Science).

The A2 pathway leads to 3 to 4°C warming by 2100.   Additional warming would occur after that, but most climate science focus ends at the end of this century.  A huge caveat applies here: that warming projection comes from models that did not represent crysophere or other processes.  This is important because the climate system is highly nonlinear.  Small changes in input can induce drastically different results.  A simple example of this is a change in input from 1 to 2 doesn’t mean a change in output from 1 to 2.  The output could change to 3 or 50, and we don’t know when the more drastic case will take place.  Given our best current but limited understanding of the climate system, 3 to 4°C warming by 2100 (via pathway A2) could occur.  Less warming, given the projected emissions above, is much, much less likely than more warming than this estimate.  Policy makers need to shift focus away from 2°C warming and start figuring out what a 3 to 4°C warmer world means for their area of responsibility.  Things like the timing of different sea level rise thresholds and how much infrastructure should we abandon to the ocean?  Things like extensive, high-magnitude drought and dwindling fresh water supplies.  These impacts will have an impact on our lifestyle.  It is up to us to decide how much.  The graphs above and stories I linked to draw this picture for me: we need to change how we approach climate and energy policy.  The strategies employed historically were obviously inadequate to decarbonize at a sufficient rate.  We need to design, implement, and evaluate new strategies.


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Climate Sensitivity and 21st Century Warming

I want to write about shoddy opining today.  I will also write about tribalism and cherry-picking; all are disappointing aspects in today’s climate discussion.  In climate circles, a big kerfuffle erupted in the past week that revolves around minutiae and made worse by disinformation.  The Research Group of Norway released a press release that somebody’s research showed a climate sensitivity of ~1.9°C (1.2-2.9°C was the range around this midpoint value) due to CO2-doubling, which is lower than other published values.

Important Point #1: The work remains un-peer reviewed.  It is part of unpublished PhD work and therefore subject to change.

Moving from that context, what happened next?  The Inter-tubes were ablaze with skeptics cheering the results.  Additionally, groups like Investor’s Business Daily jumped on the “global warming is hooey” bandwagon.  Writers like Andy Revkin provided thoughtful analysis.

Important Point #2: Skeptics view some model results as truthful – those that agree with their worldview.

IBD can, of course, opine all it wants about this topic.  What obligation to their readers do they have to disclose their biases, however?  All the other science results are wrong, except this one with which they agree.  What makes the new results so correct when every other result is so absolutely wrong?  Nothing, as I show below.

Important Point #3: These preliminary results still show a sensitivity to greenhouse gas emissions, not to the sun or any other factor.

For additional context, you should ask how these results differ from other results.  What are IBD and other skeptics crowing about?

 photo Climate_Sensitivity_500_zps9f1bcb3a.jpg

Figure 1Distributions and ranges for climate sensitivity from different lines of evidence. The circle indicates the most likely value. The thin colored bars indicate very likely value (more than 90% probability). The thicker colored bars indicate likely values (more than 66% probability). Dashed lines indicate no robust constraint on an upper bound. The IPCC likely range (2 to 4.5°C) is indicated by the vertical light blue bar. [h/t Skeptical Science]

They’re crowing about a median value of 1.9°C in a range of 1.2-2.9°C.  If you look at Figure 1, neither the median nor the range is drastically different from other estimates.  The range is a little smaller in magnitude than what the IPCC reported in 2007.  Is it surprising that if scientists add 10 more years of observation data to climate models, a sensitivity measurement might shift?  The IPCC AR4 dealt with observations through 2000.  This latest preliminary report used observations through 2010.  What happened in the past 10 years that might shift sensitivity results?  Oh, a number of La Niñas, which are global cooling events.  Without La Niñas, the 2000s would have been warmer, which would have affected the sensitivity measurement differently.  No  mention of this breaks into the opinion piece.

Important Point #4: Climate sensitivity and long-term warming are not the same thing.

The only case in which they are the same thing is if we limit our total emissions so that CO2 concentrations are equal to CO2-doubling.  That is, if CO2 concentrations peak at 540ppm sometime in the future, the globe will likely warm no more than 1.9°C.  Note that analysis’s importance.  It brings us to:

Important Point #5: On our current and projected emissions pathway, we will more than double pre-industrial CO2 concentrations.

 photo CO2_Emissions_IPCC_Obs_2011_zpsa00aa5e8.jpg

Figure 2.  Historical emissions (IEA data – black) compared to IPCC AR4 SRES scenario projections (colored lines).

As I’ve discussed before, our historical emissions continue to track at the top of the range considered by the IPCC in the AR4 (between A2 and A1FI).  Scientists are working on the AR5 as we speak, but the framework for the upcoming report changed.  Instead of emissions, planners built Representative Concentration Pathways (RCPs) for the AR5.  A graph that shows these pathways is below.  This graph uses emissions to bridge between the AR4 and AR5.

 photo CO2EmissionsScenarios-hist-and-RCP-2012.png

Figure 3. Representative Concentration Pathways used in the upcoming AR5 through the year 2100, displayed using yearly emissions estimates.

The top line (red; RCP8.5) corresponds to the A1FI/A2 SRES scenarios.  As Figure 3 shows, our historical emissions most closely match the RCP8.5 pathway.  The concentration for this pathway through 2100 is 1370ppm CO2-eq, which results in an anomalous +8.5W/m^2 forcing.  This forcing is likely to result in 4 to 6.1°C warming by 2100.  A couple of critical points: in this scenario, emissions don’t peak in the 21st century; therefore this scenario projects additional warming in the 2100s.  I want to make absolutely clear this point: our business-as-usual concentration pathway blows past CO2-doubling this century, which means the doubling sensitivity is a moot point.  We should investigate CO2-quadrupliung.  Why?  The peak emissions and concentration, which dictates the peak anomalous forcing, which controls the peak warming we face.

The IBD article contains plenty of skeptic-speak: “Predictions of doom have turned out to be nothing more than madness”, “there are too many unknowns, too many variables”, and “nothing ever proposed would have any impact anyway”.

They do have a point with their first quoted statement.  I avoid catastrophic language because doom has not befallen the vast majority of people on this planet.  Conditions are changing, to be sure, but not drastically.  There are too many unknowns.  Most of the unknowns scientists worked on the last 10 years ended up with the opposite result that IBD assumes: scientists underestimated feedbacks and results.  Events unfolded much more quickly than previously projected.  That will continue in the near future due mainly to our lack of knowledge.  The third point is a classic: we cannot act because others will not act in concert with us.  This flies in the face of a capitalist society’s foundation.  Does IBD really believe that US innovation will not increase our competitiveness or reduce inefficiencies?  Indeed, Tim Worstall’s Forbes piece posited a significant conclusion: climate change becomes cheaper to solve if the sensitivity is lower than previously estimated.  IBD should be cheering for such a result.

Finally, when was the last time you saw the IBD latch onto one financial model and completely discard others?  Where was IBD in 2007 when the financial crisis was about to start and a handful of skeptics warned that the mortgage boom was based on flawed models?  Were they writing opinion pieces like this one?  I don’t think so.  Climate change requires serious policy consideration.  This opinion piece does nothing to materially advance that goal.


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CO2 Emissions Continue to Track At Top of IPCC Range

A new Nature Climate Change editorial (subs. req.) has a very useful graph (2 variants) that I have been looking for:

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Note first the y-axis: global CO2-emissions in Petagrams of carbon per year.  This unit is different from the other common unit used: CO2 concentrations.  The emissions eventually lead to the concentrations.  This is only the CO2 emissions, not CO2-equivalent, which might be a better variable but introduces more complexity in analysis.

Let’s go through the lines on the graph before we discuss them.  The “IS92″ lines (a-f; light blue dashed) were the emission scenarios developed for the 1992 Supplementary Report to the IPCC Assessment.  There are 40 SRES scenarios shown (thin green lines) and 6 illustrative scenarios (thick green dashed lines) that the IPCC developed for the 4th Assessment Report (AR4).  These are the scenarios most people discuss: A1B, B2, etc.  For the upcoming AR5, CO2 emissions form the basis of the scenarios.  There are ways to convert from one to the other, which is how all of these different scenarios can be plotted together.  The AR5 scenarios are labeled according to the anomalous forcing value expected in the year 2100 and a “Representative Concentration Pathway”.  Thus, RCP3 represents 3 W/m^2 forcing due to CO2 concentrations.  You can see what has to happen to global emissions to achieve this relatively low forcing value by the end of the century.  Alternatively, there is an RCP4.5, RCP6, and RCP8.5 pathway.  As a side note, my work will likely utilize the RCP8.5 pathway because we will most likely continue to move down this pathway for the foreseeable future.

Historical emissions are the black dots/line.  The estimate for 2012 emissions is the red dot.  It is obvious to see that our historical emissions has tracked near the top of any set of emissions scenarios (IS92-E, IS92-F, A1FI, A2, and A1B) and not the middle or bottom.  That has implications in climate policy because most scientific studies performed to date have focused on the low to moderate scenarios.  The reason is simple: most climate scientists thought there would be no chance of inaction once people saw what was likely to happen using even low or moderate emission scenarios.  In general, scientists were wrong.  The world has continued to increase the amount of CO2 emitted into the atmosphere, with “average annual growth rates of 1.9% per year in the 1980s, 1.0% per year in the 1990s, and 3.1% per year since 2000,” as I’ve covered in 2011 and earlier in 2012.  The post-2000 increase is largely due to China and India.

The lead author of the report posted different form of this graph and included yet another call to action that the world will ignore:

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A quick note: the RCP3 scenario’s absurdity becomes more clear post-2060: emissions have to turn negative to achieve 3 W/m^2 by 2100!  Is anyone aware of technologies that remove emissions from the atmosphere in excess of what we emit to the atmosphere?  Put another way, emissions would have to decrease to near-zero in addition to deployment of removal infrastructure.  I obviously wasn’t involved scenario development, but it strikes me as incredibly myopic to include this pathway in climate scenarios: it exists only as a fantasy, especially when you realize that important feedback processes are still not understood well enough to include them in modeling efforts.

The main point of this graph is valid though: on our current emissions trajectory, global warming of 4–6.1 °C is likely.  Given recent studies showing more sensitivity to temperature changes one order of magnitude less than this that has already started to generate real-world changes, no one can say with certainty what a 4°C rise in global temperature above the pre-industrial average will cause.

Now, I must make a very important point here.  This does not mean the end of civilization or the world.  Our species is remarkably adaptive to a wide range of conditions.  While our species has never lived in a world that warm, we have enormous advantages over our ancestors: technology.  The world might not look like it does today, and we will of course not live in the same way, but I firmly believe that whatever changes we make will allow the great majority of us to continue to live.

That is not to say that we should do nothing at all.  I have made quite clear that the current approach (UNFCCC & IPCC) has proven itself to not work.  I do not know exactly what the correct approach will be, but I think remaining in a failed paradigm is a bad idea moving forward.  We must make new efforts – the more the merrier in the short-term so we can evaluate what does and does not work.  My line of thought has developed to this: I think groups must initiate smaller efforts, and indeed I think in some cases they already have.  Regional cohesive groups generally know better what works for them and why.  A good place to start on a larger scale would be to work to understand why certain actions work in some places better than others and put policies in place to exploit those opportunities.

But 2°C is not achievable by any means that I can see.  Neither is 350ppm CO2 concentration.  Scientists and activists alike should cast aside these hard to understand numbers.  A focus on other goals: energy portfolios, land use, and adaptation plans make more sense (different numbers since we tend to operate that way).

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