| Image: Created Commons under Unsplash For decades, the public has been told climate researchers understand and have accurately modeled “climate sensitivity,” defined as the average global temperature rise we should expect following a doubling of CO2 concentration in the atmosphere compared to pre-industrial levels. Yet, climate models routinely run too hot, both hindcasting (unless their outputs or the measured data is adjusted to conform) and forecasting far more warming than is actually measured by surface stations, weather balloons, and global satellites. New research from Roy Spencer, Ph.D., and John Christy, Ph.D., of the Earth System Science Center at the University of Alabama at Huntsville, published in Theoretical and Applied Climatology, concludes the Earth is not as sensitive to additions of carbon dioxide as has been assumed. Why this problem has persisted is unclear. Perhaps it is because of flawed assumptions about feedback loops, perhaps because almost no models properly conserve energy (a factor Spencer and Christy discuss in detail), perhaps because various other factors mitigating CO2 and impacting temperatures are ignored or inadequately modeled. The climate sensitivity estimates produced by current climate models range over a factor of three, from 1.8 to 5.6 degrees Celsius, in response to a doubling of atmospheric carbon dioxide. Despite 30 years of refinements and revisions and multiple iterations and versions of Coupled Model Intercomparison Project models, climate simulations have been unable to significantly close the projected gap or settle on a unified number. As a result, 80 percent of climate models project larger, steeper global warming trends over the past 50 years (since 1970) than actual observations record and trend data reveals..To try and solve this problem and produce a model that is more useful because it more accurately corresponds to real-world data, Spencer and Christy have worked for over a decade to develop a single-dimension climate model that incorporates: |
| Time-dependent forcing-feedback[s] … of temperature departures from energy equilibrium … to match measured ranges of global-average surface and sub-surface land and ocean temperature trends during 1970–2021. In response to two different radiative forcing scenarios, a full range of three model-free parameters are evaluated to produce fits to a range of observed surface temperature trends (± 2σ) from four different land datasets and three ocean datasets, as well as deep-ocean temperature trends and borehole-based trend retrievals over land. |
Their model produced a climate sensitivity estimate of 1.9℃ in response to a doubling of carbon dioxide concentrations. This is at the low end of the projected range, consistent with observational temperature data and with the projections of a small minority of existing models—models whose outputs are largely ignored as outliers by the IPCC and the most prominent alarmist climate scientists. Importantly, like existing models, Spencer’s and Christy’s model assumes all of the recent warming has been driven by human carbon dioxide emissions. Yet, as Spencer told Phys.org, “If recent warming is partly natural, it would further reduce climate sensitivity.”In the end, it seems to me that what Spencer’s and Christy’s work demonstrates most clearly is that those claiming to speak for the science of climate change still know very little about the factors that impact climate sensitivity. Climate models have been specifically developed and designed to produce one significant output: average global temperature. Ignore for the moment the fact that is a made-up metric if ever there was one. If they can’t agree on what that output should be, meaning if there is no certainty or small range for climate sensitivity across climate models, then there is certainly no reason to trust or enact public policies in response to any of the ancillary extreme weather outputs and projections that climate models forecast in response to different emission concentration pathways.In the end, science hasn’t produced a solid measure of climate sensitivity and what drives it. Science hasn’t produced and modeled concentration pathways that reflect actual emissions. Scientists can’t agree on how various forcing factors, like solar activity, clouds, large-scale ocean currents, and aerosols, actually impact temperatures, much less how to incorporate them into climate models. Scientists disagree about how various ecosystems and component parts of them might respond to warmer temperatures and what feedback loops they might produce, contributing to or detracting from general warming. And scientists, frankly, don’t know what features and physical mechanisms might remain unaccounted for, rather than just difficult to model—forcing factors or features that impact temperatures and long-term weather patterns on local, regional, or global scales that remain unknown at present. With all this in mind, climate science might be better served if climate researchers curbed their very visible hubris and, rather than speaking with confidence of an impending climate crisis absent the cessation of fossil fuel use, adopt the humility of Socrates, who is reported to have said that to the extent he was wise it was because he understood how little he actually knew, or, per Einstein, “The more I learn, the more I realize how much I don’t know.” I know the public would certainly be better served if climate scientists, rather than proclaiming the science is settled, would admit there are a lot of unknowns and because the stakes are so high, advised policymakers to proceed with caution, adopting policies that are flexible and allow adaptation in the face of an unknowable future. This piece originally appeared at HeartlandDailyNews.com and has been republished here with permission. |
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