{"id":312234,"date":"2024-03-23T15:42:30","date_gmt":"2024-03-23T14:42:30","guid":{"rendered":"https:\/\/climatescience.press\/?p=312234"},"modified":"2024-03-23T15:42:32","modified_gmt":"2024-03-23T14:42:32","slug":"uncertainty-in-natural-forcing-from-wildfire-dust-aerosols-2-times-larger-than-total-co2-forcing","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=312234","title":{"rendered":"Uncertainty In Natural Forcing From Wildfire, Dust Aerosols 2 Times Larger Than Total CO2 Forcing"},"content":{"rendered":"\n
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From NoTricksZone<\/a><\/p>\n\n\n\n

By\u00a0Kenneth Richard<\/a><\/em><\/p>\n\n\n\n

The radiative effect of natural wildfire aerosol forcing alone can be said to fully cancel out the total accumulated forcing from 170 years of CO2 increases in the current climate.<\/strong><\/p>\n\n\n\n

It has been\u00a0estimated<\/a><\/strong>\u00a0that the total change in climate forcing (radiation imbalance) from the 1750 to present CO2 concentration increase has been 1.82 W\/m\u00b2.<\/p>\n\n\n\n

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Image Source:\u00a0Feldman et al., 2015<\/a><\/strong><\/figcaption><\/figure>\n\n\n\n

New research<\/a><\/strong> suggests today\u2019s climate models omit an \u201cimportant perturbation to Earth\u2019s energy balance\u201d because they fail to include the natural climate forcing potential from aerosols produced by wildfires and dust loading.<\/p>\n\n\n\n

Climate models expressly assume this non-volcanic natural aerosol forcing is not present, or 0.0 W\/m\u00b2, even though it has been estimated that aerosol forcing from wildfire emissions alone \u2013 which were much higher during the preindustrial period before declining to today\u2019s levels \u2013 deliver a \u201cradiative effect in the current climate of -2 W\/m\u00b2.\u201d Therefore, this natural climate forcing effect can be said to, by itself, fully cancel the surface forcing from the post-industrial CO2 increases.<\/p>\n\n\n\n

Furthermore, the estimated 4 W\/m\u00b2 uncertainty in preindustrial-to-present (1850-) aerosol climate forcing from natural wildfire emissions and dust is also over two times larger than 270 years of CO2 concentration increases (1.82 W\/m\u00b2 since 1750). This effectively means that anthropogenic CO2 forcing is too uncertain to clearly separate from natural aerosol forcing.<\/p>\n\n\n\n

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Image Source:\u00a0Mahowald et al., 2024<\/a><\/strong><\/figcaption><\/figure>\n\n\n\n

Below are key quotes from this research paper.<\/p>\n\n\n\n

1) Regarding the natural aerosol forcing uncertainty missing in the models\u2026<\/p>\n\n\n\n

\u201cThe uncertainty in aerosol emissions that are usually considered natural, such as from dust storms or wildfires, is likely larger and contributes to larger uncertainties in aerosol radiative forcing.\u201d<\/em><\/p>\n\n\n\n

\u201cThere are no estimates of radiative forcing for important aerosols such as wildfire and dust aerosols in most paleoclimate time periods.\u201d<\/em><\/p>\n\n\n\n

\u201c\u2026dust deposition records [are] not captured in climate models. These models therefore also predict a dust-climate feedback that is indistinguishable from zero. As such, not explicitly accounting for dust changes as a radiative forcing has the net effect of omitting this potentially important perturbation to Earth\u2019s energy balance.\u201d<\/em><\/p>\n\n\n\n

\u201c\u2026here we are assuming, without prior information, that the radiative forcing of any paleo-time period relative to the preindustrial is around 0.0 W\/m\u00b2.\u201d<\/em><\/p>\n\n\n\n

\u201c\u2026we do not know the emissions [from wildfires or dust] well, nor the impact of those emissions on climate. We can envision these uncertainties as mostly unknown.\u201d<\/em><\/p>\n\n\n\n

2) Regarding the larger radiative forcing impact and uncertainty values of natural aerosols than CO2 forcing\u2026<\/p>\n\n\n\n

\u201cIn addition, wildfires and open fires represent some of the most important aerosols for direct and aerosol-cloud radiative effects, with a total radiative effect in the current climate of -2 W\/m\u00b2.\u201d<\/em><\/p>\n\n\n\n

\u201cThe total unconstrained uncertainty due to aerosol changes [since 1850] could be estimated as being 4 W\/m\u00b2.\u201d<\/em><\/p>\n\n\n\n

\u201c\u2026dust [radiative forcing] was likely 2-4 times higher in the Last Glacial Maximum [~25,000 to 17,000 years ago] than it is today.\u201d<\/em><\/p>\n\n\n\n

\u201cFrom the limited literature we crudely estimate a paleoclimate aerosol uncertainty for the Last Glacial Maximum relative to preindustrial [1850] of 4.8 W\/m\u00b2.\u201d<\/em><\/p>\n\n\n\n

\u201cPaleoclimate data from charcoal records suggest a maximum in open fires in the 1850s and a decrease since then. Satellite data show a global decrease in burned area over the last decades\u2026\u201d<\/em><\/p>\n\n\n\n

\u201c\u2026the 1970s is a time period of Sahel drought, and dust radiative forcing between the 1960s and 1980s changed by perhaps -0.57 \u00b10.46 W\/m\u00b2.\u201d<\/em><\/p>\n\n\n\n

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