Global land-surface warming much faster than ocean surface, and Northern Hemisphere faster than Southern: incriminates soot from burning oil and coal, exonerates CO2
Authors: Higgs Roger 
Published: February 2023

Fossil-fuel combustion now outweighs solar variations in driving climate change (Higgs 2022, GSA, www.researchgate.net/publication/362103181). Remarkably, land (near-surface-air) warming is three times faster than ocean-surface warming, and Northern Hemisphere (NH; land-ocean average) three times Southern. This aberrant behavior began abruptly in 1985 (contrast pre-1985 lockstep warming-cooling; data.giss.nasa.gov/gistemp/graphs_v4). Moreover, over land and over the NH, warming is significantly slower at altitude (UAH satellite-measured lower-troposphere average temperature).These strong lateral- and vertical warming gradients incriminate airborne soot (warms atmosphere by absorbing solar radiation). Soot&#8217;s poor dispersal causes strong concentration gradients, both (A) laterally, toward its main sources, which are predominantly on-land and NH (diesel engines, cooking woodfires, coal-fired powerplants/industries), e.g. over intensely industrialized nations (USA, Europe, China, etc.), average atmospheric soot concentration is ~1000% (i.e. 10 times) greater than over adjacent oceans (NASA 2011 global black carbon video https://svs.gsfc.nasa.gov/3844), starkly contrasting with CO2&#8217;s 1% difference (NASA global CO2 video); and (B) vertically, e.g. year-round average soot concentration above rural Siberia is ~500% higher at 0.5km than at 3km (doi: 10.3390/atmos12030351), far exceeding CO2&#8217;s 4% difference above Tokyo (10.3390/s18114064).Two further observations implicate diesel- and coal-sourced soot specifically. Firstly, 25 years (y) before the 1985 decouplings (above), world annual oil consumption tripled in 1960, then remained high almost continuously (OurWorldinData, GlobalPrimaryEnergyConsumptionBySource graph). Secondly, coal&#8217;s distinctively stepwise growth (same graph) is mimicked, with a similar time-lag (10-20y), by stepwise land-air warming (data.giss.nasa.gov/gistemp/graphs_v4): COAL GROWTH fast 1974-1989 (tripled in 1974, due to 1973 oil crisis), nil 1989-1999, fast 1999-2014 (mainly China; OurWorldinData, CoalConsumptionByRegion graph); LAND WARMING fast 1994-2005, nil 2005-2011 (famed &#8216;hiatus&#8217;), fast since 2011.CO2 cannot explain the observed strong lateral and vertical warming gradients, because its efficient dispersal produces near-homogenous atmospheric concentration. Even heavily industrial regions barely (<0.5%) exceed the global average (10.1038/s41598-019-53513-7). Furthermore, no leap in CO2 concentration occurred ~1985 or any other time; instead, CO2 grew by gradual acceleration, not stepwise (keelingcurve.ucsd.edu). Evidently, CO2 has negligible effect on climate, implying that its greenhouse effect is nullified by unknown and/or underestimated feedbacks (e.g. 10.1007/978-94-007-6606-8_17). If so, hyper-expensive CO2 capture is misconceived, besides counter-productive (today&#8217;s 420ppm is well below ~1,000ppm optimum for crop- and forest growth).In the literature, the global-warming contribution of soot (&#8216;black carbon&#8217;) is very uncertain. According to an influential review (10.1002/jgrd.50171; italic emphasis added here): &#8220;The best estimate of industrial-era climate forcing of black carbon ... is +1.1 W m-2 with 90% uncertainty bounds of +0.17 to +2.1 W m-2 (sic) ... We estimate&#160;that black carbon ... is the second most important human emission in terms of its climate forcing&#8221;. Black carbon&#8217;s warming effect was estimated to be 70% as strong as CO2. Recent IPCC estimates are 35% and 12% (2013, Physical Science Basis, Summary for Policymakers, fig.SPM.5; 2021, ditto, fig.SPM.2c). On the contrary, the data presented above suggest black carbon is overwhelmingly the dominant anthropogenic-warming agent. Helping to explain previous underestimates, two additional soot-induced warming mechanisms, via its effects on clouds, were recently recognised (10.1038/s41561-020-0631-0). Moreover, developing-world powerplants possibly emit far more soot (10.1029/1999JD900187) than the review assumed.