Seeking Cooler Than 1.5

Why 1.5ºC?

The Paris Agreement goal is to reach less than 1.5º C. It completes by the year 2100. The goal's target is to allow Earth to warm to about 1.5ºC (2.7ºF) above the average temperature from 1850-1900. Also note, 1.5ºC  is the global average: locally your town or city could warm greater than 1.5º C; it could warm more than of 10º C (or 18º F, like during the summer of 2010: "[...] anomalies were particularly pronounced, exceeding the 1970–1999 mean (18) by 10°C [... ]".) And lastly, the goal follows (economically) viable trajectory to 1.5 that includes exceeding 1.5ºC before returning to below 1.5ºC at the end of the century.

The section of my previous post, Climate Action to Carbon Removal Q&A: "Why is the amount of Carbon so much larger ..." is incorrect. The climate modeling publicly available referenced in the  Nature Article: 'Scenarios towards limiting global mean temperature increase below 1.5 °C' shows the climate returns to that of the mid-2020s or the 2000s in another graph. Because of this difference, I can't use the historical projection of radiative forcing to project the target climate. The climate of 2100 from SSPn-1.9 is more likely comparable to a climate similar to mid-2000 or mid-2020s and includes all climate extremes for those decades. Not to mention that the temperature will still rise from industrial use mid-century before finally descending to about 1.5ºC-1.4ºC. And it's worth underscoring, 1.5º C is relative to the starting timeframe of 1850-1900, per Special Report 1.5.

Figure 1. Climate Models of SSP1 1.9 IMAGE modeled by MAGICC in Green and FAIR in Purple by the IAMC Scenario Explorer hosted by IIASA

So why is the amount still so much more vast to reach 280 ppm in the atmosphere and oceans compared to only reaching a little below 1.5º C?

Think back to the original problem, we emitted Carbon Dioxide, which has accumulated in the atmosphere and oceans since the start of industry (1750). The accumulation of Carbon is roughly 460 gigatonnes of Carbon (1.8 trillion tonnes CO₂) or 80 thousand Great Pyramids of Giza, or 1.5M Empire State buildings, spread between the atmosphere and oceans. To restore the climate to a desired Carbon Dioxide concentration, we need to remove Carbon Dioxide we added that now resides in the atmosphere and oceans. We emitted about 360 gigatonnes of Carbon (1.3 trillion tonnes of CO₂) from 1750 to 2010. The target scenarios would remove on average 100 gigatonnes of Carbon (366 gigatonnes of CO₂) which has the potential to return to a climate roughly similar to 2010. Given the changes to the other greenhouse gases, the MAGICC model in Figure 1. shows a temperature more similar to what's projected for the mid-2020s. The amount to return to pre-industrial times would be the entire amount of Carbon we've emitted, all 460 gigatonnes of Carbon. This difference is perceived as politically untenable as it's perceived to be too expensive (with today's pricing of renewables and need for fossil fuels). If we wish to have the climate of say 300 ppm, we'd have to remove another 300 gigatonnes (≈1 trillion tonnes CO₂) beyond what it would take to reach 1.5ºC. To restore to a desired temperature in addition to removing CO₂, we would also need to draw down much of the short forming greenhouse gasses.

Figure 2. Cumulative Emissions are a super-exponential inducing changes to the natural sinks. SSP1 1.9 IMAGE, as well as SSP1 RCP2.6 IMAGE, are modeled for comparison. The X's listed in red are the amount of CO₂ it would take for the Atmosphere to reach 450 ppm and extrapolated to the Cumulative Emissions line. We are likely to deglaciate Antarctica when we hit 450 ppm. The SSPs splines were generated from a linear extrapolation of the SSP Database data.

No doctor would ever say to a cancer patient, 'We might be able to treat your cancer by providing the least amount of care and intervention.' That's exactly the target goal 1.5ºC primarily due to political will based on public support. It's from the support my government has historically supplied. And for that, I apologize to the world.

The UN Climate Action Summit 2019 theme referring to the climate emergency, was: 'A Race We Can Win. A Race We Must Win.' We should seek much lower than 1.5ºC should we want to secure an environment that fairly provides economic justice to all life on Earth. We didn't save the condors, bald eagles, Asian elephants, black-footed ferrets, kakapos, manatees, orangutans, the spotted owls, giant pandas, tigers, the leatherback sea turtles, the great blue whales, the humpback whales, and the redwoods, thousands square meters of rain forests, only to be lost again in another 60-100 years. We didn't decide we wanted to have Sustainable Development Goals only for the G7. A world on the brink of peril, say one created from vast amounts of CO₂; about 360 gigatonnes of Carbon (and 1.3 trillion tonnes of CO₂) similar to 2010 or that of the mid-2020s, isn't one social-ecological and economic justice.

And why? Because we're too lazy to change an existing infrastructure that delivers fossil fuels that creates wealth, and renewables are too expensive today? Those reasons aren't good enough to risk Earth for centuries to come.

Open Questions

What's the total amount of cumulative CO₂ since 1750 that equates to 450 ppm, and other tipping points? What scenarios get us away from these tipping points the fastest? What temperature relative to 1850, is safe and acceptable warming, that provides environmental justice for all plant, animal life on Earth? Note this allowable warming is relative to a point in time that was changed by human emissions, therefore this number could be negative. What's the fastest, safest rate we can remove Carbon from the atmosphere to restore the climate the fastest?

Climate Action to CDR Q&A

Image Credit: CC-BY 4.0 Shannon Fiume, 2018 https://bit.ly/2V3qP80


How much Carbon do we need to pull out of the air (and oceans) to get to a Carbon Dioxide concentration of 281 ppm, as it was in the pre-Anthropocene?
   As of late last year by the latest emissions figures reported by the Global Carbon Budget Project, we need to pull about 460 gigatonnes of Carbon or remove 1.6 trillion tonnes of Carbon Dioxide from the atmosphere.

And what’s the fastest rate could we pull this out of the atmosphere?
   This question isn’t simple, as we don’t know what’s the optimal rate to pull Carbon out of the atmosphere. Here are some hypotheticals. If were to remove all Carbon from human emissions, in the next twenty-five years, we’d need a fast rate of removal, say slightly over 18 gigatonnes of Carbon (or about 67 gigatonnes of CO₂) per year. If we expect to reach restoration in a somewhat longer time, say 30 to 40 years, then that number could lower. If we want to finish by 2100, when many of us have died, then we can reduce that number even further. If we lose the carbon sequestration capacity of the land sink, meaning the Carbon trapped underground or in plants goes into the atmosphere and subsequently pushed into the ocean, then the total goes up. We actually should plan on the amount being high initially such to steer us clear of tipping points.

Why are tipping points bad?
   There are large deposits of Carbon locked up in frozen methane, ice, and permafrost. Should these large quantities of Carbon get released quickly in a matter of years, or less, it will radically increase global warming. There are other tipping points, such as removing large amounts of ice cover, which would also quickly increase global warming. This radical increase in warming presents a much more difficult path where Carbon Dioxide Removal (CDR) is theoretically not able to keep pace with warming. For CDR to be successful, we need to get to emission neutral and practice removal to stop the planet from warming enough to set off the tipping points.

Why is the amount of Carbon so much larger than the figure quoted by the United Nations Intergovernmental Panel on Climate Change and popular press?
   The way to lower Earth's temperature is estimated by the UN IPCC in climate models that break down many hypotheticals ways into scenarios, and some of them target to not exceed 1.5º C. Their reports use a measure of heat named Radiative Forcing, which is Watts per area of gas or body such as Earth. The lowest amount of allowable warming to not exceed 1.5º C is RF 1.9 W/m². (Outlined in the technical science reports global modeling teams use different software to model how to achieve RF 1.9 W/m². The data from these team's scenarios are used to generate the probability of attaining below 1.5º C.) Reaching 281 ppm would be a Radiative Forcing of 0 W/m² and 0º C of allowed warming. Reaching a Radiative Forcing of 1.9 W/m² would be akin to reaching the climate of 1984, whereas a Radiative Forcing of 0 would be a climate just after the mini-ice age/global cooling in the 1790s.¹ (Search for 1984 in the previously linked NOAA reference page.) (This section is incorrect, and is corrected in this blog post: Seeking Cooler than 1.5ºC.)


How do we get to the climate of the 1790s and why 281 ppm?
   We need everyone to do everything in Project Drawdown to get us nearly emission neutral and get involved in CDR and carbon tech. 281 ppm was the global average Carbon Dioxide concentration from 600 BCE to 1750. We need scientists to identify if 281 ppm is the optimum Carbon Dioxide concentration. We don't know what the optimum Carbon Dioxide concentration is.

Scatter plot of Antarctic Ice Core CO₂ concentration data from multiple ice cores: Law Dome, Dome C, Maud, Taylor Dome, WAIS Divide, Vostok, and the 

South Pole from the time of 200,000 BCE to 2004 CE. The pale green line is the mean of 280.9 from 600 BCE to 1750 CE.

By when do we need to hit Carbon neutral or emission neutral?
   We need to hit emission neutral ASAP, not by 2030, or later, but as fast as humanly possible. We need to start carbon removal as soon as humanly possible to steer Earth’s climate clear of tipping points. We ought to hit double-digit gigatonnes of Carbon removed in the next couple of years. We have to scale an industry that doesn’t exist.

Go back to the safety of this much removal, how safe is it?

   At this point, we don’t know. We need scientific labs to find the upper limit of how fast we can remove Carbon and not cause the climate to fall into a mini ice-age. We need labs to identify what’s the slowest we can remove and not set off the tipping points, and not have the climate extremes like the present time. While labs are working to find the fastest and safest rate, since it takes time to scale the technologies to remove gigatonnes; we need entrepreneurs, scientists, and engineers to create, enhance, and scale CDR technologies.

What can we do, how can we take climate action?
   We need everyone to create, extend, and scale renewables and CDR technologies. We’ll need many early adopters to buy or try open CDR solutions. We'll need everyone to switch to the renewable option asap. These efforts will get the economic engine to prefer recycled-emissions carbon-based goods. And we need everyone to get involved in CDR now, and so we can go carbon negative!

¹ In the paper Alternative Method to Determine a Carbon Dioxide Removal Target, as well as in "A solution to the misrepresentations of CO2-equivalent emissions of short-lived climate pollutants under ambitious mitigation", the historical RF precedent is used to substantiate temperature in the place of generating a model.