V. (Ram) Ramanathan | PAS Academician

Climate Resilience: Why, When and How?

Summary and Recommendations

Summary of Data: Climate change is no longer a problem that is in the distant future; it no longer is a problem that affects just those in the margins of society. It has become a disruptive phenomenon affecting all aspects of society, including social, economic, and agricultural systems, and disrupting terrestrial and marine ecosystems. The number of weather/climate/water-related disasters has increased five-fold during the last 50-year period.


  • We can no longer rely just on mitigation of climate change but must broaden the framework of climate actions to include adaptation and transformation. In this broader framework of Climate Resilience, social and natural systems must be transformed to become climate resilient.
  • Climate resilience actions must consider two other interrelated major crises: Unsustainable loss of biodiversity; and unsustainable inequality among people and nations.
  • Championing and enacting mitigation actions to reduce climate risks needs to be the primary objective of the wealthiest one billion population, while implementing climate adaptation measures must be the primary focus of the poorest three billion.
  • The planet will most likely cross the 1.5°C warming threshold in 8 to 12 years (2030 to 2034). Limiting warming to 2°C or slightly lower is still an achievable goal. Adaptation measures need to plan for warming of at least 2°C.
  • A major effort focused on the poorest three billion people must be immediately initiated to adapt to the impacts of climate change and provide: 1) access to affordable clean energy and water; 2) help to farmers impacted by droughts and heat stress with improved governance and technical assistance to shift to drought-resilient agriculture;3) integration of technological solutions with nature-based solutions; 4) improved access to health care to cope with mental as well as physical health effects.

Resilience: What is it?

Resilience has a wide spectrum of interpretations. IPCC [1] goes on to define Resilience as follows:

Resilience in this report is defined as the capacity of social, economic and ecosystems to cope with a hazardous event or trend or disturbance, responding or reorganizing in ways that maintain their essential function, identity, and structure as well as biodiversity in case of ecosystems while also maintaining the capacity for adaptation, learning and transformation.

IPCC [1] elaborates on the above definition by stating: “Resilience as a system trait overlaps with concepts of vulnerability, adaptive capacity, and thereby risk, and resilience as a strategy overlap with risk management, adaptation, and also transformation”.

Climate resilience needs to be built on three pillars: First Pillar – Mitigation to reduce climate change risks; Second Pillar – Adaptation to reduce exposure and vulnerability to climate changes that are unavoidable; and Third Pillar – Transformation of society to develop the capacity to prepare and plan for mitigation and adaptation. This transformation needs to happen bottom-up from the level of an individual and a community to national level.

Climate Resilience: Need for a new framework to address climate risks

  • Climate change is no longer a problem that is in the distant future; it no longer is a problem that affects just those in the margins of society. It has become a disruptive phenomenon affecting all aspects of society, including social, economic, and agricultural systems and disrupting terrestrial and marine ecosystems. The number of weather/climate/water-related disasters has increased five-fold during the last 50-year period [2].
  • Bending the warming curve quickly is a global imperative. Since we have delayed too long to bend the emissions curve, bending the warming curve requires more ambitious actions in addition to deep cuts in carbon emissions. Both the emissions and the warming curves are rising unsustainably. Fossil fuel emission of CO2 reached its highest value in 2021.
  • The warming crossed the 1°C threshold around 2014. The planet is currently warming at an unprecedented rate and is very likely to amplify by 50% (from 1°C) and cross the 1.5°C threshold in 8 to 12 years, during 2030 to 2034 [3]. This is likely to become the COVID moment for the climate crisis, affecting everyone on the planet directly or indirectly. Without deep emission cuts, the warming can cross the dangerous threshold of 2°C in about 25 years [1, 3]. The velocity of changes is already posing severe constraints and limits on adaptation [1]. Currently, 50% of the world population is subject to severe water shortages and 3.3 billion people live in countries with high climate vulnerability [1].
  • We can no longer rely just on mitigating climate change but must broaden the framework of our climate actions to include adaptation. In this broader framework of Climate Resilience, social and natural systems must be transformed to become climate resilient.

Finally, climate resilience actions must consider two other interrelated major crises: Unsustainable loss of biodiversity [4]; and unsustainable inequality among people and nations. There are amplifying feedback effects between the three crises, such that solving one of them will have co-benefits for the other two.

Climate Resilience: Criteria setting Context

Inequality: There is a vast inequality among the global population in terms of income, wealth, access to energy, water, healthcare, and other resources. It is helpful for this discussion to divide the population into three groups [5]: The wealthiest 15% of the population, which is currently about 1 billion. I refer to this group as the Top One Billion (T1B). The poorest 40% of the population, which is about 3 billion, referred to as Bottom Three Billion or B3B. In between the two, is the middle 45%, or about 4 billion, M4B. The uncertainty in these demographic statistics is at least 10%. For example, the 40% cited for B3B can range from 36% to 44%.

Per capita income of the poorest three billion, B3B, is less than $10/day (US dollars) and that of the middle 4 billion is between $10/day to $30/day, i.e., about 85% of the population earns less than $30/day [6]. The combined wealth of the B3B is about 2%, and that of the top one billion is 76% [6]. The poorest three billion rely on primitive fuels (wood, dung and solid coal) and technologies (mud stoves, open burning, kerosene) for cooking, heating, and lighting.

The top one billion contribute about 50% or more of the climate warming pollution, such as CO2, methane and HFCs. On the other extreme, the 3 billion in the B3B contribute only about 7%. Among the 3 billion in B3B, the poorest 0.7 billion emit just 0.5% of the CO2 pollution [6].

On the receiving end of the climate risks, climate change impacts are felt disproportionately by the B3B, living mostly in rural areas. Over the last forty years, extreme weather has led to a cumulative 606,000 mortalities and 4.1 billion displaced people [7]. Global warming has decreased the GDP of the bottom three billion by 17% to 31% [8].

Globally, agriculture productivity decreased by 21% due to climate change and climate pollution [9]. An extreme case is India, where the warming and fossil fuel-related air pollution decreased wheat yield by 34% [10]. One of the main reasons is that the warming (and related drying) impacts those (most of the B3B population) living in hotter areas more than those (more than half of T1B population) living in equitable climates. In short, climate impacts act as force multipliers of the underlying socio-economic-cultural forces that cause inequality.

Global climate mitigation actions must be championed and enacted by the T1B group to limit climate risks to manageable levels, even for the B3B and M4B groups; implementing climate adaptation measures (through T1Bs technological/financial support) must be the primary goal of the B3B.

Near and Long Term: Our main concern is the 21st century, although climate changes, once initiated, can last thousands of years due to the millennial time scales of ice sheets and ocean circulation. The near term applies to the period until 2050 and the long term beyond 2050. This categorization of the time scales is motivated by the fact that unchecked warming can exceed the 2°C guard rail for catastrophic climate risks by 2050, and deep reductions to the emissions of CO2 and other heat-trapping gases to near-zero levels must happen by 2050. Beyond 2050, failure in drastic mitigation actions can lead to catastrophic/unmanageable warming levels of 3°C or more [1,3] that could lead to crossing of various tipping points in the social and natural systems.

The primary goal is to limit the warming below 2°C by 2050 and beyond, which is still an achievable goal.

Inertia in the social and the natural systems: There are numerous sources of inertia which pose severe constraints on the efficacy of mitigation actions. Let us start with the inertia in the social system: 1) Time it takes for society to respond to scientific findings; 2) Time it takes for policy makers to respond to societal concerns; 3) Time to adapt available technologies and develop new ones for reducing emissions and the time for global scaling. Inertia from the above three sources can range from ten to fifty years. Next comes the inertia in the natural systems.

Once emitted, heat trapping gases stay in the atmosphere for about a decade (methane and HFCs) to several decades (CFCs) to a century (nitrous oxide) and even longer (carbon dioxide). The ocean-land-atmosphere system has thermal inertia such that about 1/2 to 2/3 of the projected warming (that results from today’s emissions) is delayed by about 10 to 15 years and the remaining 1/3 to 1/2 will unfold over multi-decadal to longer time scales.

Because of these sources of inertia, the crossing of the 1.5°C warming in the next 8 to 12 years is mostly assured irrespective of the mitigation actions that are being contemplated currently.

We can still limit the warming below 2°C, provided we start bending the emissions curve in the next five years, which requires the entire global society to pull simultaneously on three levers (illustration below).

Building Climate Resilience: The Three Pillars

The First Pillar: Mitigation. We have waited too long to make deep cuts. The T1B must reduce their own emissions and provide financial as well as technological assistance for the rest of the world to follow their example.

Bending the warming curve below 2°C by 2050 requires society to pull on three levers [11; 12] as illustrated above:

  1. The Short-lived climate pollutants (methane, HFCs, surface and lower atmosphere ozone & Black Carbon soot) lever. With available technologies and current air-pollution governance mechanisms, we can cut the emissions of these pollutants by 40% to 100% within 25 years and cut the rate of warming by half.
  2. The Decarbonization lever. We must bring down the fossil fuel-related emissions of CO2 close to zero before 2050; This is the most important step for keeping the warming below 2°C for the rest of the century and beyond.
  3. The Atmospheric Carbon Extraction (ACE) lever. The blanket of carbon dioxide is already too thick (it weighs 1.1 trillion tons already and we are emitting about 40 billion tons every year). From now to 2050, we must extract as much as 300 billion tons of CO2 out of the air and thin the heat-trapping blanket sufficiently.

The Second Pillar: Adaptation. The first step is to reduce vulnerability and exposure to weather extremes and other severe risks such as sea level rise and ocean acidity that are already occurring. Biodiversity loss and degradation of coastal and other ecosystems caused by climate change are also major risks. The next step, much more daunting, is to develop plans for future climate changes. To give but one example of its daunting nature, with unchecked emissions, the warming will progressively increase from 1.5°C to 2°C to 3°C etc. during the 21st century. Should adaptation planners, target 1.5°C, 2°C or 3°C or more? My best guess is that we should plan for 2°C warming for the time being and update it as needed, in about five to ten years from now.

While mitigation starts with and relies on top-down policies, adaptation measures require a different approach. It must start at the individual to local community level and integrate scientific knowledge with knowledge of local cultures and local governance mechanisms. Adaptation also must rely on top-down actions on a national to global level to deal with long-term risks such as sea level rise, ocean acidity and biodiversity loss. Several sectors are impacted (Figure above reproduced from [13]) with agriculture and infrastructure topping the list.

A major effort focused on marginalized and vulnerable populations, especially the B3B, must be immediately initiated to adapt to the impacts of climate change. It must provide: 1) access to clean energy and drinkable water for all; 2) help to farmers suffering from droughts and heat stress around the world with improved water and land governance, enhanced water storage and technical assistance to shift to drought-resilient agriculture; 3) integration of technological solutions with nature-based solutions; 4) climate change poses grave threats to human health, including mental health. Improved access to health care for the B3B and M4B should be prioritized.

The Third Pillar: Transformation

The third pillar of resilience is transformation of society and ecosystems. Transformation, instead of incremental transitions, can change the fundamental attributes of natural and social systems. To give but one example, growth in GDP is strongly coupled with energy generation and consumption. Transformation would involve decoupling energy consumption from economic growth, by increasing energy efficiency, reducing energy waste, and reducing the carbon intensity of energy consumption. On the social side, behavioral changes for reducing consumption and working for the common good are going to be essential attributes for climate risk reductions. Another example is a socio-economic transformation that will enable equitable access to renewable energy and natural resources for all and preserve the ecosystem and biodiversity for generations to be born. Such singular transformations require massive education of everyone from children to senior citizens, so that they will collectively support drastic and bold actions by their religious, cultural, social, and political leaders.

I will conclude with the most formidable challenge of all, which is uncertainty. There is uncertainty in societal will to bend the emissions curve; uncertainty in the magnitude of the future warming and resultant impacts, due to the multitude of feedbacks between and within the human and natural systems. Compounding all these uncertainties is the uncertainty in the optimal responses by society. We have an obligation not to let uncertainty paralyze us to inaction. Since uncertainty can go both ways (i.e., make it much worse or much better), use the uncertainty to catalyze rapid actions. It is going to require multiple iterations where we learn in the field by experimentation to sort out better actions [14]. Climate scientists have a special role to help society navigate through the uncertainties, provided scientists and scientific institutions form alliances with governments, private sector, faith-based institutions and NGOs who are on the front lines of climate actions.


1)   Intergovernmental Panel on Climate Change (IPCC), 2022. Climate Change 2022: Impacts, Adaptation and Vulnerability. Publishers: WMO and UNEP: https://www.ipcc.ch/working-group/wg2/
2)   World Meteorological Organization (WMO), 2021: WMO Atlas of Mortality and Economic Losses from Weather, Climate and Water Extremes (1970–2019), WMO-No. 1267. https://library.wmo.int/index.php?lvl=notice_display&id=21930#.Yq9RTC-B2kE
3)   Y. Xu, V. Ramanathan, & D.G. Victor. 2018. Global warming will happen faster than we think. Nature, vol. 564, 30-32.
4)    National Academies of Sciences, Engineering, and Medicine (2022). Biodiversity at Risk: Today’s Choices Matter. Washington, DC: The National Academies Press. https://doi.org/10.17226/26384
5)    Ramanathan, V. (2014), The Two Worlds Approach for Mitigating Air Pollution and Climate Change. In Sustainable Humanity, Sustainable Nature, Our Responsibility, Proceedings of the Pontifical Academy of Sciences and Pontifical Academy of Social Sciences Workshop, ES 41, ISBN 978-88-7761-108-6 https://www.pas.va/en/publications/extra-series/es41pas.html
6)    Chancel, L., T. Piketty, E. Saez, G. Zucman (2022). World Inequality Report 2022. Published by World Inequality Lab, wir2022.wid.world. https://wir2022.wid.world/www-site/uploads/2021/12/WorldInequalityReport2022_Full_Report.pdf
7)    The United Nations Office for Disaster Risk Reduction (2016). The Human Cost of Weather-Related Disasters 1995-2015. https://www.unisdr.org/files/46796_cop21weatherdisastersreport2015.pdf
8)     Orttiz-Bobea Ariel, T.R. Ault, Carrillo C.M., Chambers R.G., D. Lobell (2021). Anthropogenic climate change has slowed global agricultural productivity growth. Nature Climate Change, 11, 306-312.
9)     Diffenbaugh, N.S., and M. Burke (2019). Global Warming has increased global economic inequality. PNAS, 116, 9808-9813.
10)  Burney, J., and V. Ramanathan (2014). Recent climate and air pollution impacts on Indian agriculture, Proc. Natl. Acad. Sci., 111(46), 16319-16324.
11)  Ramanathan, V., Molina, M.L., Zaelke, D., and Borgford-Parnell, N. (2020). Well Under 2°C: Ten Solutions for Carbon Neutrality and Climate Stability. Health of People, Health of Planet and Our Responsibility. Springer International Publishing. https://doi.org/10.1007/978-3-030-31125-4
12)  Ramanathan, V, Y. Xu & A. Versaci (2021): Modelling human–natural systems interactions with implications for twenty-first-century warming. Nature Sustainability, https://doi.org/10.1038/s41893-021-00826-z
13)  United Nations Environment Program, 2021: Adaptation Gap report 2021: The gathering storm- Adapting to climate change in a post-pandemic world. https://www.unep.org/resources/adaptation-gap-report-2021
14)  Sabel, C.F., D.G. Victor (2022). Fixing the Climate, Princeton University Press.

Acknowledgments: I am thankful for financial support from the Frieman foundation at UCSD and from Cornell University and for comments on the text by Prof. David Victor of UCSD.