A surprising revelation from a new paper: industrial emission actually have a net cooling effect on Earth's climate. The paper that appears in the Proceeding of the National Academy of Sciences early edition attempts to apportion blame for global warming among various economic sectors. Climate impacts of CO₂, tropospheric ozone, fine aerosols, aerosol-cloud interactions, methane, and long-lived greenhouse gases were all analyzed and the appropriate human activities cited. When the dust settled, two sectors turned in large net negative (i.e. cooling) forcing values: biomass burning and industry.

Contrary to what many believe, not all human activity causes global warming. This new report, “Attribution of climate forcing to economic sectors,” was authored by Nadine Unger and colleagues from NASA GISS, the Center for Climate Systems Research at Columbia University, the University of Illinois, Lawrence Berkeley National Laboratory, and the Environmental Defense Fund. Motivation for this work is put forth in the paper's abstract:

A much-cited bar chart provided by the Intergovernmental Panel on Climate Change displays the climate impact, as expressed by radiative forcing in watts per meter squared, of individual chemical species. The organization of the chart reflects the history of atmospheric chemistry, in which investigators typically focused on a single species of interest. However, changes in pollutant emissions and concentrations are a symptom, not a cause, of the primary driver of anthropogenic climate change: human activity. In this paper, we suggest organizing the bar chart according to drivers of change—that is, by economic sector.

Instead of blaming CO₂ or ozone (O₃) the goal was to let people know just how harmful various human activities are to the climate. Among the activities considered were animal husbandry, home fuel use, aviation and agriculture. “Because sector profiles differ greatly, this approach fosters the development of smart climate policy and is useful to identify effective opportunities for rapid mitigation of anthropogenic radiative forcing,” state the authors. What a shock to discover that industrial activity, one of the primary targets for green activists world wide, is not causing the planet to warm after all.

As can be seen from the figure below, taken from the paper, there is a lot of variation from sector to sector. But several important human activities have net forcings that are almost in balance (agriculture and aviation) or negative (agricultural waste burning and shipping). But the biggest contributors to global cooling are biomass burning and industry, with net radiative forcings of -106 and -158 mWm^-2 respectively.

Radiative forcing grouped by sector in 2020. From fig 1 of Unger et al.

The cause of the counterbalancing cooling is primarily ascribed to AIE, aerosol indirect effect, though airborne sulfates and organic carbon also play a part. Radiative forcing due to the effects of aerosols on clouds that include indirect effects and semi-direct effects are all counted as part of aerosol indirect effect. Other aerosol effects that might cause warming, such as black carbon on snow albedo, are not included in AIE. While the authors are sure that, by 2100, darn near everything people do will cause global warming, the modeling results shown above should hold for the next decade or so.

What implications does this surprising revelation have for mitigation efforts and industrial policy? “Caution must be taken in reducing emissions from the industry sector since this action will considerably accelerate near-term warming,” concludes the paper. In other words, shutting down industry any time soon will cause the planet to warm, not cool. A similar situation would occur for reducing emissions from biomass burning, so the next time someone complains about people burning wood or dung to clear fields or cook their food think again.

When it comes to analyzing climate forcings things are often not as they might first appear. Industry, through aerosol emissions, is the single major force opposing global warming according to this study. And the number one emitter of CO₂, power generation, has three quarters of its warming impact offset by aerosols as well. We don't need geoengineering schemes to inject aerosols into the atmosphere, all we need are more factories. As long as we have industrial smokestacks belching particulates into the atmosphere we can breath easy about global warming—just be careful not to breath too deeply.

Be safe, enjoy the interglacial and stay skeptical.

The first line of defense against global warming—just don't breath too deeply.