The Sars-Cov-2 pandemic came in a time when people were showing growing concern about inequality, discrimination, and climate change. The large uneven shock to the global economy amplified some of those concerns. The pandemic has increased global poverty for the first time in over 20 years, has disproportionately affected women, and the global distribution of vaccines has been rolled out according to the wealth of nations.
At the same time, the sudden stop of the global economy was followed by a dramatic, and somewhat obvious, decrease of greenhouse gas emissions (GHG). Changes in mobility, consumption and production drove this decline in emissions. After rising steadily for decades, global carbon dioxide emissions fell by 6.4% (or 2.3 billion tonnes), which was larger than the decrease in global GDP (estimated at around 4.5%). This suggests that highly GHG intensive activities were more affected by the economic slowdown. In the tourism and aviation industries, for example, losses are estimated at 4 trillion USD dollars  and 126 USD billion, respectively. For the latter, that is nearly four times the loss caused by the 2008 financial crisis.
The sharp reduction in GHG caused by the pandemic begets a reckoning. Is it possible to resume economic activity, restore growth paths, and at the same time, limit the recovery of GHG?
The United Nations Environment Programme (UNEP) has estimated that the world would need to cut carbon emissions (which represent the largest share of GHG) by 7.6% per year for at least the next decade to prevent the globe from warming more than 1.5 ºC above pre-industrial levels —a goal set in the 2015 Paris climate agreement. 
Over the previous two decades, the carbon intensity of the global economy has decreased –which means that more GDP has been produced with fewer emissions. In 1990, a tonne of CO2 would generate USD 2265; by 2019, just before the pandemic, a tonne of CO2 would produce USD 3580.  This represents an increase of 58% in 29 years. While welcome, this decline in carbon intensity of the global economy needs to be vastly accelerated.
The airline industry provides a case study. There have been important technological improvements in the airline industry in terms of carbon emissions: in 1950, the industry would emit 2.5 kg/km for each passenger; by 2018, the number was 125gr/km per passenger —one twentieth of the number in 1950. Technological improvements have also been present in the ground transportation industry and yet GHG emissions more than doubled between 1970-2014. This increase also reflects vast inequalities. According to the IPCC, around 10% of the population account for 80% of the distance travelled through motorized vehicles. 
The pandemic provides an experiment of reduction in emissions in the airline industry. Using the dataset from the OpenSky Network,  we estimate that in 2019 the air transport industry consumed 185 Tg of fuel, equivalent to 585 tonnes of CO2.  Taking 2019 as the baseline, it is possible to calculate the differences in 2020 due to the pandemic. In total, 364 tonnes of CO2 were produced during 2020. This is 221 tonnes of CO2 less than in 2019 (a decrease of 42.43%).
The significant reduction of emissions in aviation, as in other transportation industries, shows that it is possible to limit human activities that are highly polluting without compromising income to the same extent. As the decrease in the carbon intensity of the global economy shows, economic growth is not inevitably linked to environmental damage. On the contrary, mainly through an increase in disasters —which could result in trade disruptions and failing productivity— economic growth will be severely affected as the consequences of climate change worsen. Via measures like better regulations, public and private investments in less GHG intensive activities, inter-sector dialogue, post-pandemic reconstruction must seize the opportunity created so as not to return to the previous emissions trajectory and reach the commitments of the Paris Declaration. We have a unique chance to build fairer economies, while safeguarding our planet for future generations. Yet GHG emissions are already returning to pre-COVID levels. The opportunity to accelerate the reduction of GHG started by the pandemic should not be missed. 
 United Nations Conference of Trade and Development (UNCTAD) and UN World Tourism Organization (UNWTO). (June, 2021), “Covid-19 and Tourism”
 UNEP. (2019), “Cut global emissions by 7.6 percent every year for next decade to meet 1.5°C Paris target – UN report” [online], available at https://www.unep.org/news-and-stories/press-release/cut-global-emissions-76-percent-every-year-next-decade-meet-15degc
 OWID. [online], available at https://ourworldindata.org/grapher/co2-emissions-and-gdp. USD are 2017 constant international
 Sims R., R. Schaeffer, F. Creutzig, X. Cruz-Núñez, M. D’Agosto, D. Dimitriu, M.J. Figueroa Meza, L. Fulton, S. Kobayashi, O. Lah, A. McKinnon, P. Newman, M. Ouyang, J.J. Schauer, D. Sperling, and G. Tiwari. (2014), “Transport” in Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, United Kingdom and New York, Cambridge University Press [online], available at https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5_chapter8.pdf
 We also used the methodology set out in “Fuel Estimation in Air Transportation: Modeling global fuel consumption for commercial aviation” published in Transportation Research, to convert the fuel burn of different types of aircraft to GHG.
 The difference from the estimate of 733 Tg noted above is most likely due to limitations in coverage of the OpenSky Network sensor network.
 See Oxfam, 2020 “Confronting carbon inequality, Putting climate justice at the heart of the COVID-19 recovery”.