Abstract. The growth rate of greenhouse gas (GHG) climate forcing increased rapidly in the last 15 years to about 0.5 W/m2 per decade, as shown by the “colorful chart” for GHG climate forcing that we have been publishing for 25 years (Fig. 1).[1] The chart is not in IPCC reports, perhaps because it reveals inconvenient facts. Although growth of GHG climate forcing declined rapidly after the 1987 Montreal Protocol, other opportunities to decrease climate forcing were missed. If policymakers do not appreciate the significance of present data on changing climate forcings, we scientists must share the blame.
Our approach to climate analysis places highest priority on data. Climate forcing (see the definition at the end of this communication) by GHGs is a good place to start, as it is the drive for global warming. GHG amounts are well-measured. Our calculated forcings are in close agreement[2] with those of IPCC and we also agree with IPCC that the uncertainty in absolute GHG forcing is about 10%.[3] We show the 60-month (5-year) running-mean of GHG forcing change (Fig. 1) to smooth out short-term variability of sources and sinks of the gases. Thus, results for the last 2.5 years are shaded, because they are <60-month means and will therefore change as more data are added, likely decreasing the current peak value a bit. [HGs are 45 halogenated gases, including the HGs covered by the Montreal Protocol and other HGs.]
One implication of the increased growth rate of GHG forcing in the last 15 years is that the goal to keep global warming under 2°C is now implausible. IPCC defined a GHG scenario (RCP2.6) intended to provide a 66% chance of keeping global warming below 2°C. Actual growth of GHG forcing has diverged dramatically from that scenario (Fig. 1), with reality being close to the extreme RCP8.5 scenario. The gap between reality and RCP2.6 could be closed by capturing and storing CO2 (carbon capture and sequestration, CCS), but the annual cost for the gap at January 2023 (the time of the last 60-month mean) would be $2.4-5 trillion[4] with current technology, and the gap and annual cost are increasing.
RCP2.6, in fact, was never plausible, as it relied on assumption of large-scale biomass-burning at powerplants with carbon capture and permanent storage of the captured CO2, a scheme that would ravage nature and threaten food security.[5] We scientists must share the blame, if we allow policymakers to believe that such scenarios provide a realistic projection of climate change.
Missed opportunities to phase down the growth of GHGs are worth understanding because that knowledge can aid development of future policies. Useful information on climate change and energy policy was already available in 1988, when IPCC was formed. Global reserves of conventional fossil fuels (coal, oil, gas) clearly were enough to cause climate change, albeit of uncertain magnitude. The science community had been asked, at least implicitly, if it made sense to develop unconventional fossil fuels to succeed coal, oil, and gas as a major source of world energy. The famous Charney report[6] on climate change was requested by the Science Adviser of U.S. President Jimmy Carter because of concern about potential climate effects of Carter’s plans for coal gasification and the fossil fuel industry’s budding efforts in hydrofracturing of rock formations (fracking) to extract “tight” oil and gas. In subsequent decades, scientific concern about the threat of human-caused climate change grew continually.
Given a desire to limit fossil fuel emissions, economics recognizes superiority of honest pricing as the efficient means to achieve change, as opposed to arbitrary political dictates. The price of fossil fuels should include their costs to society, which implies the merit of a slowly rising carbon fee to achieve competition among clean energies, energy efficiency, and carbon capture. Instead, the 1997 Kyoto Protocol and 2015 Paris Agreement are precatory (wishful thinking) agreements to try to reduce future emissions. The Paris meeting was preceded by substantial effort to inform the delegates about the need for a simple, honest, rising, carbon fee, but the response of the Executive Secretary of the United Nations Framework Convention on Climate Change dismissed this with “(Many have said) we need a carbon price and (investment) would be so much easier with a carbon price, but life is more complex than that.”[7] In fact, a carbon price is the simple approach; it only requires agreement of the nations with largest emissions; it can be made near-global by border duties on products from nations without a carbon price. The reason a global carbon price does not exist is that governments are under the corrupting thumb of special interests and give little weight to the interests of young people and future generations.
A second missed opportunity, although less fundamental than the failure to promote a carbon fee or tax, is egregious because it was self-inflicted by the COP (Conference of the Parties) process. In 2001 at COP 6-2 in Bonn, Germany used its position as host nation to push through exclusion of nuclear power from support as a Clean Development Mechanism (CDM). Indeed, failure to support development of nuclear power as a carbon-free source of energy was widespread. In President Bill Clinton’s first State-of-the-Union speech after the 1992 United States election, he announced that research and development of nuclear power was unnecessary and would be terminated. Almost unlimited subsidy of renewable energies was adopted in many U.S. states and some other nations via “Renewable Portfolio Standards,” requiring utilities to obtain a growing fraction of their energy from renewable energies. This approach, as contrasted with “Clean Energy Portfolio Standards,” spurred the development of natural gas as the complement to intermittent renewable energy, and, as a consequence, expansion of fracking, pipelines, and methane leakage. Nuclear power, given the costs of the fuel and materials to build a power plant, has potential to be the least expensive among the firm, dispatchable, energy sources, but attainment of its potential, as with other sources, requires extensive R&D and experience. Thus, it is ironic that the COP now suddenly asks for nuclear energy output to be tripled.[8]…
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