Weatherdem's Weblog

Bridging climate science, citizens, and policy


1 Comment

Commercialized Carbon Removal

The Guardian has an interesting article about startups working on capturing carbon dioxide from the air – a necessary technology if we are serious about any kind of climate goal with less CO2 than our business-as-usual pathway.  What are the companies doing and why is it important?  The article highlights three businesses: Carbon Engineering, Global Thermostat and Climeworks, which started in the 2000’s.  “All are aiming to make low-carbon fuels, used recycled CO2 and renewable energy to power the process.”  They’re making low-carbon fuels because small markets for them already exist.  Those markets will have to increase in size and scope for these startups to grow.

That’s one important aspect.  Another is the so-called “climate goal”.  As stated by international groups and increasing numbers of scientists, the climate goal is keeping CO2 concentrations below a certain threshold in order to keep global temperatures from increasing above 2C.  There is another international climate conference scheduled for later this year – the Conference of Parties in Paris, France (COP-21).  Leading up to that conference, countries are submitting carbon reduction goals that can be internationally monitored and verified.  Goals stated so far will definitely not meet the <2C goal – read about the UK’s goals here, for example, or here about the 45 countries who submitted plans already.  The reason is simple: we cannot deploy enough renewable energy generation or institute enough efficiency measures or change fuel types fast enough that will translate into halving global CO2 emissions within 10 years and going net negative by 2050.

What these companies are doing is directly related to that last goal: net negative CO2 emissions.  It won’t happen by 2050 or any other year unless we push serious money into research, development, and deployment.  It will take the private and public sectors working together for decades for utility-scale CO2 withdrawal from fuel burning and the free atmosphere.  These companies, and others, are the forefront of that industry.  But they need capital – a lot of it.  Cashflow at this juncture of their existence is crucial for them to exist long enough to deploy their technologies and evolve them as they run in the real world.  Anyone have a spare million or so dollars sitting around?


Leave a comment

Some Short Notes on the US-China Climate Deal

The US-China climate deal announced in December 2014 generated big news.  It was yet another diplomatic success for the Obama administration and John Kerry’s State Department.  Nothing I say below takes away from that success.  In terms of climate action success, the deal ranks pretty low to me.  I’ll quickly summarize what I understand of the deal and then share why I think it isn’t a significant climate deal.

The Deal

Here is a quick summary (emphasis mine):

China, the world’s biggest emitter of greenhouse gases, pledged in the far-reaching agreement to cap its rapidly growing carbon emissions by 2030, or earlier if possible. It also set an ambitious goal of increasing the share of non-fossil fuels to 20 percent of its energy mix by 2030.

Obama announced a target to cut U.S. emissions 26 to 28 percent below 2005 levels by 2025 – eight years after he leaves office — the first time the president has set a goal beyond the existing 17 percent target by 2020.

The bolded portions highlight the agreement’s big news.  China agreed to a carbon emissions cap and the U.S. pushed its emissions reduction target out 5 years and increased the target by ~11% below 2005 levels.

Those are good goals.  Are they sufficient goals?  It depends on what you consider sufficient.  I consider goals that will actually achieve the stated climate target of <2C warming by 2100 as sufficient.  These goals won’t achieve that target.  But then, as I’ve written for some time now, I don’t think we can set goals that achieve the <2C by 2100 target.  There are technical and political hurdles that we chose not to surmount during the past 30+ years.  Why won’t this agreement achieve that target?  Let’s take a quick look from the same International Business Times article:

China completes a new coal plant every eight to 10 days, and while its economic growth has slowed, it is still expanding at a brisk rate exceeding 7 percent.

The scale of construction for China to meet its goals is huge even by Chinese standards. It must add 800 to 1,000 gigawatts of nuclear, wind, solar and other zero-emission generation capacity by 2030 — more than all the coal-fired power plants that exist in China today and close to the total electricity generation capacity in the United States.

And to meet its target, the United States will need to double the pace of carbon pollution reduction from 1.2 percent per year on average from 2005 to 2020 to 2.3 to 2.8 percent per year between 2020 and 2025.

Who out there truly believes that China can deploy 800 GW of zero-emission generation capacity in less than 15 years?  Remember before you answer in the affirmative that China’s deployment of coal-fired plants exceeded anything in history and that coal remains an extremely cheap energy resource.  All the other technologies currently cost more in terms of deployment.  What incentives does China, as a developing nation, have to spend more money for intermittent power sources?  They’re more interested in growing their economy, as the U.S. is.  Speaking of the U.S. – I emphasized part of that quote quite purposefully to highlight the scale of the issue.  China must, in 15 years, deploy as much generation infrastructure as exists in the entire U.S. today.  Our infrastructure took decades and decades to build out.  China needs to do the same thing, with more expensive infrastructure, in 15 short years!?  I will be among the first to congratulate China if they accomplish this daunting task and I don’t think China should shy away from working towards it.  I just don’t think they have a realistic chance of actually accomplishing it.

What about the U.S.?  We need to more than double the decarbonization rate of our economy to achieve our emissions goals.  Remember that most of the decarbonization achieved since 2005 was due first to the Great Recession and second to the natural gas boom.  The Great Recession is finally behind us, though effects linger.  The natural gas boom?  It’s currently experiencing strong headwinds as OPEC pushes the cost of oil down to the $50 range from the $100-110 range last year.  It’s economically unfeasible to frack for natural gas with $50 per barrel of oil.  While the natural gas industry won’t collapse (at least I hope it doesn’t), it won’t support additional decarbonization for the foreseeable future either.

I believe we are well on our way toward 3-4C warming by 2100 and must plan and act accordingly.  This deal, while diplomatically ambitious, is not climate ambitious enough to drive us away from those thresholds.


Leave a comment

Deep Decarbonization Pathways Interim Report Released

An international group of folks put together an interim report analyzing “Deep Decarbonization Pathways”.  Decarbonization refers to the process of using less carbon within an economy.  The intent of the report was to show ways forward to keep global mean temperatures below 2C.  Readers of this blog know that I no longer think such a goal is achievable given the scope and scale of decarbonization.  We have not moved from a “business-as-usual” approach and have run out of time to reduce GHG emissions prior to relevant limits to meet this goal.  I argue the exact opposite of what the authors describe in their summary:

We do not subscribe to the view held by some that the 2°C limit is impossible to achieve and that it should be weakened or dropped altogether.

Thus the main problem with this report.  They’re using a threshold that was determined without robustly analyzing necessary actions to achieve it.  In other words, they a priori constrain themselves by adopting the 2C threshold.  Specifically, a more useful result would be to ascertain what real-world requirements exist to support different warming values in terms real people can intuitively understand.  The report is not newsworthy in that it reaches the same results that other reports reached by making similar assumptions.  Those assumptions are necessary and sufficient in order to meet the 2C threshold.  But examination unveils something few people want to recognize: they are unrealistic.  I will say that this report goes into more detail than any report I’ve read to date about the assumptions.  The detail is only slightly deeper than the assumptions themselves, but are illuminating nonetheless.

An important point here: the authors make widespread use of “catastrophe” in the report.  Good job there – it continues the bad habit of forcing the public to tune out anything the report has to say.  Why do people insist on using physical science, but not social science to advance policy?

On a related note, the report’s graphics are terrible.  They’re cool-color only, which makes copy/paste results look junky and interpretation harder than it should be.  So they put up multiple barriers to the report’s results.  I’m not sure why if the intent is to persuade policy makers toward action, but …

Continue reading


Leave a comment

Distopias are not Preferable to Distopias

Grist’s Nathanael Johnson has a good article up discussing the Anthropocene – a term that describes Earth influenced by mankind.  I highly recommend reading it, then thinking through what Andy Revkin and Clive Hamilton discussed.

I for one disagree with Clive Hamilton’s language.  Some examples:

I don’t accept this idea that we consumers in the West are irrevocably attached to cheap energy.

This from a person in Australia (dominant energy source: cheap coal) using 1st world technology to talk with Johnson and Revkin across the planet using Skype.  Those technologies are also powered, by and large, by cheap energy.  He continues with:

It’s easy for us in the US and Australia to forget that some countries in Europe have less than half — a third — of our emissions per person. And with strong public support, I’m thinking of Germany here, for policies that cut emissions. I think Western consumers can quite easily be weaned off high-polluting energy sources.

This ignores easily verified objective data that shows if the developing world used German-level energy, global energy consumption would triple or quadruple.  The developing world, like the developed, will expand energy production as cheaply as possible – and that means fossil fuels.  How will we meet stated climate goals with 3x more dirty energy?   Moreover, the West has not weaned itself from high-polluting energy sources.  If it was easy, we would have done it by now.  If we want to achieve the deepest emissions cuts pathway modeled by the IPCC, we need one 1GW carbon-free energy plant to come online every day between now and 2050.  That simply isn’t happening.

Or we can look at it with open eyes, and allow it to blast away all our utopian imaginings, and say, well, we are in really deep trouble, and it’s extremely unlikely that we are going to get out of it unscathed. So what do we do in that situation? And what does it mean for how we act? Does it mean we go for the muddle-through approach even though we know the consequences are likely to be catastrophic? Or do we fundamentally try to rethink and change strategies?

The “utopian imaginings” Hamilton refers to are solidly based in reality.  They are projections that new technologies will allow people in the future access to low-polluting energy at prices lower than today.  These technologies include renewables, carbon capture and sequestration, and things we can’t envision today because they haven’t been invented.  That’s not utopian.  By analogy, Hamilton would have said in the 1880s that mechanized transport will never exist and so stop imagining utopia.  But I also have problems with his characterization that we “are in really deep trouble”.  This is based on the concept of “civilization collapsing” and “catastrophe”.  I have written at length against this language since I read social science peer-reviewed literature that using it immediately makes people shut down anything else you have to say.  Thus, Hamilton and others continue to accomplish exactly the opposite of what they want.

Thankfully, Johnson immediately followed up with what Hamilton’s suggestion might look like.  You know, suggest something practical and not purely philosophical.  Hamilton’s response:

I don’t have an answer to that, Nate, except to say the first thing we must do is face up to the facts.

This is the fundamental problem for climate activists in my opinion.  They don’t have practical suggestions for solutions.  But they want everyone else in the same disaster-based landscape that the activists are in.  Only after everyone is miserable and paralyzed can we talk about ways forward.  This is not the solution.  Or it’s not my solution, anyway.  I just wrote a post about what happens when you present facts to people without the appropriate context.  In that example, N.C. residents directly challenged “the facts”.  And instead of long-term sea-level policy, N.C. now has short-term sea-level policy because a Commission did what Hamilton suggests without offering practical ways forward.  There isn’t evidence that Hamilton can be persuaded on this, as he ends with this:

It’s a question of a bad or less bad Anthropocene.

Good luck getting people to react to that in ways that advance a clean energy future.  Because history quite clearly tells us it won’t happen any time soon.  Hamilton in this instance advocates for a distopia while disdaining others’ viewpoints because he thinks they are distopian.  We should not replace one for the other.


1 Comment

2014 US National Climate Assessment Released

The US Global Change Research Program issued its latest National Climate Assessment today. There are lots of goodies in it.  I want to focus on a couple of things that caught my eye in an initial skim.

Impacts will increase in frequency and severity (no big surprise there). This assessment includes up-t0-date research results on those impacts.  Like most reports, they leave `Responses` as a final category.  I understand the logic of laying out the evidence of climate change and its impacts prior to discussing solutions, but as I’ve written before today, people primarily respond to solutions and not problems.  Only the most dedicated readers will make it all the way through the report to get to the Response section.  My worry is that the Response section will not be the focus of activists’ attention; a continuation of decades of wasted energy.

Extreme Weather

The report summarizes the state-of-the-science well: “Over the last 50 years, much of the U.S. has seen increases in prolonged periods of excessively high temperatures, heavy downpours, and in some regions, severe floods and droughts.”  That is accurate.  I do not think one example is valid, however.  The report discusses anomalous warmth and dryness in Texas and Oklahoma in 2011.  I do not argue that the event occurred; I blogged about it and the subsequent 2012 Great Plains drought.  Where I deviate from the Assessment is this: there is scant evidence that the 2011 Southern Plains drought had a strong climate signal.  The same goes for the 2012 Great Plains drought.  Instead, these droughts were strongly linked to drier summertime conditions during the recent decade as part of a regime shift, most probably due to natural decadal variability (Hoerling et al. 2014).  The 2011 Texas heat wave was more likely to occur than it was 40 years ago.  This is not the same thing as identifying a clear attribution – something that remains at the cutting edge of climate science.

Likewise, the largest determinant of Atlantic hurricanes remains natural variability.  The Assessment’s statement that Atlantic hurricane activity increased since the early 1980s is true, but there are important details to consider.  The Atlantic signal is opposite the global signal (a small reduction in overall hurricane activity in that same time period), so regional effects are important to consider.  The Atlantic Multidecadal Oscillation is currently in a positive phase (since the early 1980s – isn’t that interesting?), which includes a warmer than usual Atlantic Ocean.  All else equal, this facilitates tropical storm development, which we’ve seen.

The Assessment’s conclusion stands in direct contrast to a couple of peer-reviewed papers, including Chylek and Lesins 2008 (we find no increase in the number of major hurricanes (category 3–5); If there is an increase in hurricane activity connected to a greenhouse gas induced global warming, it is currently obscured by the 60 year quasi-periodic cycle.) and Enfield and Cid-Serrano 2009 (Projections to the year 2025 show that the cumulative change in summer warm pool size since 1975 will depend critically on whether a subsequent cooling in the multidecadal cycle occurs, comparable to the warming between 1975 and 2000 AD.)  In other words, determining how man-made warming affects Atlantic hurricanes will not be detectable from the natural signal for many years to come.

That doesn’t mean we do nothing.  To the contrary, I argue that we need to adapt our current infrastructure to our current climate.  Multi-billion dollar events occur today.  Most of that is related to increases in population and wealth, as the Assessment reports.  We can lessen impacts by hardening our infrastructure (taking the likeliest climate effects into account) today while simultaneously mitigating future climate effects.  One should not happen without the other, but at a minimum, we need to adapt to today’s climate while recognizing tomorrow’s climate will be different.

Southwest

I want to cite the impacts the Assessment identifies for the Southwest, which includes California, Nevada, Utah, Colorado, New Mexico, and Arizona.  This region is the hottest and driest of the US.  They include: “increased heat, drought, insect outbreaks, and wildfires.  Declining water supplies, reduced agricultural yields, health impacts in cities due to heat, and flooding and erosion in coastal areas are additional concerns.”

Key messages:

  • Reduced snowpack and streamflow
  • Agricultural threats
  • Increased wildfire
  • Sea level rise
  • Heat threats to health

Southwest Responses

I really want to highlight one of the responses.  Without having read through all the responses carefully, I want to point out that I hope other responses are better than this one.  The selected response shows one scenario that could theoretically achieve 80% GHG reductions from 1990 levels by 2050:

 photo SW_energy-generation-by-2045_12447_v10-hi_0_zps2c73bc2c.jpg

I’ll discuss Colorado here; the Assessment included references to exhaustive reports for California, which I’ll cover in the future.

The latest data for Colorado’s net generation shares (2012) demonstrate the immense challenge confronting the scenario shown above.  Broken down by percentage: coal (64.3%), natural gas (20.1%), wind (11.2%), hydroelectric (3.7%), solar (0.3%), biomass and other (0.1% each).  The scenario above (still trying to pin down units) shows that wind can become the dominant source of electricity generation.  In principle, I agree.  But wind would have to switch places with coal as the dominant generation type by 2050 to achieve 80% GHG reductions.  Wind has penetrated the electricity generation market, which I fought for and applaud.  But it still trails natural gas (1/2 the generation) and significantly trails coal (1/5 the generation).  Changing those ratios requires a policy upheaval which I don’t think is likely.  Renewables will eventually supplant fossil fuels as primary generation technologies.  At this time, I don’t think it will happen in Colorado or anywhere else (California has an outside shot) by 2050.

Conclusion

This Assessment is useful for academics and activists, but is probably not useful for the general public.  A brief review of the Response section didn’t convince me that the writers and editors had the public as their primary audience.  I’ve seen Twitter explode today with comments regarding how people were at the forefront of this report, how actionable the information is, etc.  I’m not convinced yet.  Hopefully that will change.


1 Comment

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.

Follow

Get every new post delivered to your Inbox.

Join 364 other followers