Emissions of greenhouse gases, principally carbon dioxide (CO2), are driving rapid climatic changes including rising temperatures, altered precipitation patterns, sea level rise, and increased frequency of extreme weather events (IPCC, 2021).
Under business-as-usual scenarios, these changes are projected to have widespread adverse impacts on natural ecosystems, agriculture, water resources, human health and livelihoods. However, scenarios aimed at limiting future warming to 1.5-2°C above pre-industrial levels require rapid and far-reaching transitions in energy, land use, infrastructure and industrial systems (Rogelj et al., 2018). Achieving these transformations represents an enormous challenge.
Thus, discourse on climate change often emphasizes either boredom at the prospect of incremental solutions or eco-anxiety at the vast scale of the problem. However, there are also reasons for optimism. This paper reviews 10 such reasons, highlighting pathways towards climate change mitigation.
Reason 1: Peak Emissions
Global CO2 emissions from fossil fuel combustion and industrial processes have more than doubled since 1980, rising from 15.7 to 36.7 gigatonnes per year (Gt/yr) in 2019 (Friedlingstein et al., 2022). However, several major economies have already reached peak emissions over this period. Emissions peaked in 2007 in the United States (US) at 6.0 Gt/yr, in 1988 in Russia at 2.4 Gt/yr, in 2013 in Japan at 1.4 Gt/yr, and in 1979 in the European Union (EU) at 4.3 Gt/yr (Liu et al., 2020).
Under current policies, global emissions are projected to peak around 2025 at 37 Gt/yr according to the International Energy Agency (IEA, 2021). Earlier and lower peak emissions would further limit climate change risks. Much depends on the trajectories of China and India, which respectively account for 28% and 7% of global emissions (Friedlingstein et al., 2022) and are still experiencing population and economic growth. However, China has committed to peak emissions before 2030 and achieving carbon neutrality by 2060 (UNFCCC, 2021), with some analyses suggesting this could occur even earlier given rapid renewable energy deployment (Yuan et al., 2022).
Reason 2: Decarbonization of Economic Growth
As countries develop economically, emissions initially rise rapidly but subsequently peak and decline – a phenomenon known as the environmental Kuznets curve (Stern, 2004). This reflects both structural economic changes towards less emissions-intensive sectors and the implementation of climate policies with rising incomes. Consequently, emissions associated with a unit of economic output tend to fall over time – a process known as decarbonization of economic growth.
From 1990 to 2019, the carbon intensity of gross domestic product (GDP) declined by 1.9% annually in the US and by 2.4% annually in the EU (World Bank, 2022). Assisting developing countries, especially rapidly growing economies like India, in leapfrogging towards less emissions-intensive development pathways will be crucial to bend the global emissions curve (Kartha et al., 2022).
Reason 3: Renewable Energy Growth
Renewable energy sources are achieving rapid growth, increasing from 2.6% of global primary energy supply in 2010 to over 5% by 2019, with solar and wind constituting most of this share (IEA, 2021). Costs of solar and wind power have declined dramatically, becoming cheaper than new coal or gas plants in most of the world (IRENA, 2022).
If scaled up sufficiently, renewables have the potential to drive deep emissions reductions. Analyses suggest that solar and wind energy could cut global energy and industry emissions by up to 8 Gt/yr in 2050 – greater than the combined current emissions of the US and EU (BloombergNEF, 2021). However, growth rates must accelerate, with solar and wind energy needing to expand globally by 2030 at two to five times the pace of the past decade (IEA, 2021).
Reason 4: Nature-based Solutions
In addition to clean energy transitions, protecting and restoring natural carbon sinks like forests and soils can provide over one-third of cost-effective climate mitigation through 2050 (Griscom et al., 2017). Ending deforestation and restoring degraded forests, croplands, wetlands and grasslands could reduce emissions by 5-7 Gt/yr, equivalent to the total current emissions from either Africa or South and Central America, at costs potentially less than $50 per ton of CO2 (Griscom et al., 2017; Roe et al., 2021).
Numerous companies, governments and non-profits have made commitments towards these goals as part of initiatives like the UN Decade on Ecosystem Restoration. One of the most ambitious efforts is Africa’s Great Green Wall, which aims to restore 100 million hectares of currently degraded land by 2030 (Great Green Wall, 2022).
Reason 5: Energy Efficiency
Transitioning to more efficient appliances, lighting, vehicles, building designs and industrial equipment can also substantially reduce energy demand and associated emissions. Studies estimate that implementing the best available technologies for cooling, lighting and other end-uses could cut emissions by 4.5 Gt/yr in 2050 (IEA, 2021).
Progress is already underway in many countries. For example, between 2000 and 2018 efficiency gains led to a 15% reduction in average energy use per household in the EU despite rising ownership of appliances (EC, 2020). However, tapping the full potential requires policy support as more efficient technology choices often have higher upfront costs.
Reason 6: Emerging Solutions
Research towards new emissions reduction and carbon removal solutions is rapidly expanding (National Academies, 2019), aiming to overcome hurdles around cost, scalability and environmental impacts. One study identified over 2,500 closed mines globally that could provide underground storage for 280 billion cubic meters of renewable energy in the form of heat or compressed air (Li et al., 2022). This exceeds annual global electricity generation, providing a potential solution for intermittency and storage barriers for solar and wind power. Other emerging options range from direct air capture to low-carbon concrete manufacturing to cultivated meat (WMO, 2021). While most are not yet commercially viable, continued innovation can enable these solutions to play a greater role by mid-century.
Reason 7: Species Recovery Success Stories
Biodiversity loss represents a global crisis, with over 1 million species threatened by extinction due to factors including habitat destruction and overexploitation (IPBES, 2019). However, there are also examples of successful species recovery efforts, often through relatively simple and low-cost interventions (Hoffmann et al., 2010). Population recovery programs for endangered species like the black robin in New Zealand, Arabian oryx in the Middle East or golden lion tamarin in Brazil have prevented extinction through captive breeding and reintroduction (Groombridge et al., 2004).
Nest box provisioning or protection has aided recovering numbers of burrowing owls in Canada, barn owls in the UK and wandering albatrosses globally (COSEWIC, 2006; Taylor, 1994; Weimerskirch et al., 2022). While biodiversity challenges remain severe, these cases highlight that extinction is not inevitable even for highly threatened species.
Reason 8: Paris Agreement Momentum
Before 2015, global climate policy lacked a unified international framework, with the 1997 Kyoto Protocol only covering developed countries. However, at the 2015 Paris Climate Conference 196 countries adopted the first universal, legally binding global agreement to limit climate change (UNFCCC, 2015). The Paris Agreement set out goals to hold warming well below 2°C and ideally below 1.5°C above pre-industrial levels. Although current country pledges remain insufficient for these targets, the agreement provides a ratcheting mechanism to increase ambition over time (UNEP, 2021).
Already, projected warming under current policies has reduced from over 4°C in early assessments to approximately 3°C today (Climate Action Tracker, 2020). If fully implemented, submitted pledges could plausibly hold warming below 2°C (Rogelj et al., 2016). The business community has also largely embraced climate action, with one-fifth of the world’s 2000 largest public companies now committed to net-zero emissions (EY, 2022).
Reason 9: Single-use Plastics Momentum
Plastic pollution has emerged as a highly visible environmental challenge, with single-use plastic waste a particularly problematic component entering water bodies and ecosystems (Borrelle et al., 2020). However, after years of citizen campaigns, over 100 countries have now adopted total or partial bans on lightweight single-use plastic bags, alongside levies on other single-use plastics in some cases (UNEP, 2018).
For example, England implemented charges on single-use bags in 2015, reducing usage by over 95% (DEFRA, 2021). Initial results suggest other countries are observing similar demand reductions, although effective waste management systems are also crucial to prevent unintended consequences like increased usage of other single-use items.
Reason 10: Climate Justice Mechanisms
While climate change impacts will be uneven, with developing countries and vulnerable populations experiencing harm disproportionate to their emissions contributions, frameworks for distributing climate action obligations and funding support remain complex and contested (Okereke & Coventry, 2016; Holz et al., 2018). However, in March 2022 over 130 United Nations member countries adopted a landmark resolution focused on climate justice (UNGA, 2022).
The resolution requests the International Court of Justice to clarify state obligations regarding the climate emergency. It also reaffirms that more economically developed countries holding greater historical responsibility should assume ambitious emissions reductions and provide finance, technology and capacity building to poorer countries. If implemented effectively, such efforts can help balance equities and capabilities in the global climate response.
Conclusions
In summary, while the scale of decarbonization required to meet Paris Agreement goals remains daunting, this review has identified 10 reasons for cautious optimism. Peak emissions have already occurred in several major economies. Global carbon intensity of economic output is declining over time. Renewable energy and nature-based solutions offer cost-effective emissions reduction potentials of over 10Gt/yr each by mid-century. Continued energy efficiency gains, emerging breakthrough technologies, species recovery programs, international agreements, reduced plastic pollution and climate justice mechanisms provide further building blocks.
With unprecedented cooperation, ambition and follow-through on existing solutions, the Paris Agreement targets could still be within reach. However, time is short for action. Under most scenarios, global emissions need to approximately halve this decade and hit net zero around mid-century (IPCC, 2022). Technological change and policy support must accelerate dramatically in the 2020s to achieve these transformations (IEA, 2021). Failure to marshal efforts could lock the world into devastating warming trajectories. But success could demonstrate how collective human ingenuity and global cooperation can overcome even existential threats. The future remains undetermined – but grounds for guarded optimism exist.
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