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Bridging climate science, citizens, and policy

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April 2018 CO2 Concentrations: 410.26 ppm

During April 2018, Scripps University measured an average of 410.26 ppm CO2 concentration at the Mauna Loa, Hawai’i Observatory.

This value is important.  Why?  Because 410.26 ppm is the largest CO2 concentration value for any April in recorded history.  The unending trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.

When I wrote about this topic a few years ago, there were no monthly or annual CO2 averages that exceeded 400 ppm.  In the intervening time, concentrations passed that threshold.  Actually, monthly CO2 concentrations have not fallen below 400 ppm since Jan 2016; the same thing can be said for annual concentrations since 2015.

How do concentration measurements change during calendar years?  The following two graphs demonstrate this.


Figure 1 – Monthly CO2 concentration values (red) from 2014 through 2018 (NOAA).  Monthly CO2 concentration values with seasonal cycle removed (black).


Figure 2 – 60 year time series of CO2 concentrations at Mauna Loa Observatory.  The red curve represents the seasonal cycle based on monthly average values.  The black curve represents the data with the seasonal cycle removed to show the long-term trend.  This graph shows the recent and ongoing increase in CO2 concentrations.  Remember that as a greenhouse gas, CO2 increases the radiative forcing of the Earth, which increases the amount of energy in our climate system.

CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming.  Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere.  Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries.  Human systems do not yet exist that remove CO2 from any medium (air or water) at a large enough scale to make a difference to planetary CO2 concentrations.  CO2 removal systems are not likely to exist for some time.  I’ve written a sentence like that for nearly a decade now.  Unfortunately, NOAA will extend the right side of the above graphs for years and decades to come.

CO2 concentrations rise when there is more CO2 emitted into the Earth system than removed from it.  Recently, humans have only increased the CO2 emission rate, which means that CO2 concentrations have to rise, absent carbon sinks becoming more efficient.

The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will.  It depends first and foremost on the rate at which we emit CO2 into the atmosphere.  We can choose 400 ppm or 450 ppm or almost any other concentration target (350 ppm seems out of reach within the next couple hundred years).  That choice is dependent on the type of policies we decide to implement.  It is our current policy to burn fossil fuels because we think doing so is cheap, although current practices are massively inefficient and done without proper market signals.  We will widely deploy clean sources of energy when they are cheap, the timing of which we have some control over.  We will remove CO2 from the atmosphere if we have cheap and effective technologies and mechanisms to do so, which we also control to some degree.  These future trends depend on today’s innovation and investment in research, development, and deployment.



GHG Emissions: 2C Remains a Fantasy

In the post-Paris Accord climate world, analysis of theoretical scenarios that have a reasonable likelihood of keeping global temperatures “only” 1.5°C warmer than pre-Industrial have become all the rage (one of the latest examples I’ve seen).  I’ve written posts about the mythology associated with 2°C scenarios given the reality of countries’ CO2 emissions historically.  Given that reality, 1.5°C scenarios reside further in the realm of fantasy.

The primary reason is the lack of scalable technologies to remove CO2 from the atmosphere.  That is not a judgment statement, it is an observation about how things exist in the real world.  Theoretical studies have their utility.  My ongoing anxiety revolves around policy makers’ dependence on those studies to inform their decision making.

The resources required to deploy global-scale renewable or nuclear energy are mind-boggling enough.  If we need to add to that infrastructure additional technologies that remove CO2 from the atmosphere, it strikes me as obvious that we need to be sober about our expectations to do so.

For the record, decisions like the Canadian government’s to purchase the Kinder Morgan’s Trans Mountain pipeline for C$4.5bn (US$3.45bn) will result in higher future requirements to deploy additional renewable energy and CO2 removal technologies.  They make it harder to achieve the already fantastical targets that many climate activists are focused on.  The decision ensures that the recent plateau in CO2 emissions will remain a historical anomaly:


Set in the context of future emission scenarios, the decision should be framed more as one that locks us into a warmer global future:


To have any hope of a <2°C world, global CO2 emissions need to peak.  They haven not done so as of 2017 and likely will not in 2018 or in the following handful of years, absent some financial or geopolitical disaster.  The right hand time series is clear: if we continue emitting anywhere near 35-40 GTCO2 every year, it becomes increasingly likely global temperatures will rise to 3-4°C by 2100.

The difference between 1.5°C and 2°C sounds very small to most people.  The impacts of that small difference are actually big:


The impacts are what policy makers are responsible for.  And this infographic does not show what impacts are likely at 3°C or 4°C.  We can attribute this lack of information to the aforementioned excessive focus on 1.5°C and 2°C by the research community.  It will be hard to decide on climate policy moving forward if we are not appropriately informed about the risks that today’s decisions are locking in.