by F. Menton, Oct 25, 2023 in ClimateChangeDispatch
It’s by far the most important scientific question of our age: Do human emissions of CO2 and other such “greenhouse gases” cause significant global warming, aka “climate change”?
Based on the belief that an affirmative answer to that question is a universally accepted truth, our government has embarked on a multi-trillion dollar campaign to transform our economy by, among other things, eliminating hydrocarbon fuels from electricity generation (without any demonstrated workable plan for the replacement), outlawing the kinds of vehicles we currently drive, suppressing fossil fuel extraction, banning pipeline construction, making all your appliances work less well, and much more. [emphasis, links added]
Express any doubt about the causal connection between human activities and climate change, and you could very well get labeled as a “climate denier,” fired from your academic job, demonetized by Google or Facebook, or even completely ostracized from polite society.
But is there actually any real proof of the proposition at issue? In fact, there is not.
I had two important posts on this subject back in 2021: one from January 2, titled: “Causation Of Climate Change, And The Scientific Method,” and the other from October 28, titled: “ ‘The Climate Is Changing And Human Activities Are The Cause’: How, Exactly, Do We Know That?”
See also: To what extent are temperature levels changing due to greenhouse gas emissions?
by K. Richard, Nov 10, 2022 in NoTricksZone
An increase in effective radiative forcing from human activity is now said to be mostly driven by a decline in aerosol pollution, superseding the effects of CO2 emissions.
The majority of an alleged acceleration in anthropogenic global warming in the 21st century “is driven by changes in the the aerosol [effective radiative forcing] trend, due to aerosol emissions reductions” (Jenkins et al., 2022).
Estimates of the anthropogenic effective radiative forcing (ERF) trend have increased by 50% since 2000 (+0.4W/m2/decade in 2000-2009 to +0.6W/m2/decade in 2010-2019), the majority of which is driven by changes in the aerosol ERF trend, due to aerosol emissions reductions. Here we study the extent to which observations of the climate system agree with these ERF assumptions. We use a large ERF ensemble from IPCC’s Sixth Assessment Report (AR6) to attribute the anthropogenic contributions to global mean surface temperature (GMST), top-of-atmosphere radiative flux, and aerosol optical depth observations. The GMST trend has increased from +0.18°C/decade in 2000-2009 to +0.35°C/decade in 2010-2019, coinciding with the anthropogenic warming trend rising from +0.19°C/decade in 2000-2009 to +0.24°C/decade in 2010-2019. This, and observed trends in top-of-atmosphere radiative fluxes and aerosol optical depths support the claim of an aerosol-induced temporary acceleration in the rate of warming. However, all three observation datasets additionally suggest smaller aerosol ERF trend changes are compatible with observations since 2000, since radiative flux and GMST trends are significantly influenced by internal variability over this period. A zero-trend-change aerosol ERF scenario results in a much smaller anthropogenic warming acceleration since 2000, but is poorly represented in AR6’s ERF ensemble. Short-term ERF trends are difficult to verify using observations, so caution is required in predictions or policy judgments that depend on them, such as estimates of current anthropogenic warming trend, and the time remaining to, or the outstanding carbon budget consistent with, 1.5°C warming. Further systematic research focused on quantifying trends and early identification of acceleration or deceleration is required.
by K. Richard, Nov 5, 2020 in NoTricksZone
The forcing uncertainties and lack of observational measurements in the top-to-bottom global ocean preclude an assessment that modern warmth is due to anthropogenic activities.
Key points from a new paper (Gebbie, 2021):
• 93% of the changes to the Earth’s energy budget, manifested as warming of the Earth system, are expressed in the global ocean. Just 1% of global warming is atmospheric.
• Even with the advent of “quasi-global” temperature sampling of the ocean since 2005 (ARGO), these floats “do not measure below 2,000-m depth.” This means that temperature changes in “approximately half the ocean’s volume” are still not being measured today.
• To detect the effects of anthropogenic forcing, it would require energy budget imbalance measurement precision of 0.1 W/m² at the top of the atmosphere (TOA). Uncertainty in the forcing changes affecting climate are ±4 W/m², meaning that uncertainty is about 80 times greater than an anthropogenic signal detection.
• Past changes in global ocean heat content, such as the last deglaciation, have been 20 times larger than modern changes.
• Ocean heat storage during the Medieval Warm Period (Medieval Climate Anomaly, or MCA) was much greater than modern. Modern global ocean heat uptake is “just one-third” of what is required to reach the levels attained during Medieval times.