What factors determine the resilience of the full set of interacting ecosystem services that support human well-being and allow for adaptation to a changing environment?

This question requires interdisciplinary research among physical, biological and social sciences. It raises significant conceptual or theoretical issues, as well as significant needs for empirical research at global and regional scales. The question quickly gives rise to a host of important more specialized questions. Answers to this family of questions are relevant for applied questions of sustainability science.

Definitions: (1) Resilience is the capacity of a system to persist within thresholds or “guardrails”, adapt to changing circumstances, or transform to something new when the current mode of operation is unsustainable. (2) Ecosystem services are benefits that people receive from nature, such as provision of food and water, regulation of water flows and quality, and cultural values. They can be analyzed at the global scale or for specific landscapes and seascapes.

Challenges: A key challenge is that changes in ecosystem services generally have strong correlations. That is, changes that cause increases in one group of ecosystem services often cause decreases in another group of ecosystem services. These tradeoffs among bundles of ecosystem services are not well understood. In management, they lead to unintended adverse consequences. These consequences often take systems across thresholds, degrade resilience, and impair the capacity of the system to respond adaptively to future environmental changes. Thus understanding the tradeoffs has fundamental importance for sustainable management.

Obstacles: In order to address this question, new frameworks for interdisciplinary collaboration are needed. Also there are significant needs for conceptual development, theoretical research, monitoring at global and regional scales, and empirical research at global and regional scales.

What is the exact sensitivity of the climate system to changing greenhouse gas, dust and aerosol loading in the atmosphere?

The IPCC AR4 has shown that, although we understand better and better how the climate system works, there are still considerable uncertainties in evaluating its future evolution. Not only due to uncertainties in human emissions, but also because of flaws in our physical and biogeochemical understanding of the system. The unpredicted recent evolution of Arctic sea ice or of the Greenland ice sheet are magnificent examples of such flaws.

Although everyone legitimally wants to understand the impacts of climate change (which drives many other global changes such as water resources, biodiversity, agriculture, extreme events, etc…), or wants to develop strategies of mitigation and adaptation to global change, there is little hope in doing a good job in the two latter aspects of global change if one does not improve our physical understanding of the system.

Climate sensitivity is the clear prerequisite to all other physical aspects such as tipping points, feedbacks, thresholds, etc… Solving this question allows one to basically improve the response to all other questions, from the physics to the mitigation, going through the impacts.

How and why did genuine global changes happen? What were their local and global consequences on the physical environment, the ecosystems and the societies? What thresholds are involved?

Without paleoclimatic information, we would not know that atmospheric CO2 can vary naturally by up to 100 ppm on glacial-interglacial times, that abrupt climatic changes did occur on annual or decadal scales, that ice sheets may disrupt very rapidly, and basically that climate can change at all. These testimonies of how our Earth system is functioning are invaluable, yet still quite sparse and often not so well understood. They will likely deliver numerous further surprises. A great variety of climatic changes occured in the past, with many different amplitudes or consequences, and on many different time scales. When exceeding some thresholds, they were able to induce changes on the environment of past ecosystems and societies. These events should be traced back and quantified, before we can claim that we are in a position to predict future changes and their impacts.

How long can the Earth System sustain the present rate of human-induced global-environmental change?

Humans are modifying the planet at an alarming rate. Cropland and pasture now cover almost 50% of the entire land surface. This has led to massive habitat destruction, fragmentation and pollution and, together with overhunting, is causing a critical loss in biodiversity. Agricultural pollution is also having a devastating impact on aquatic and marine ecosystems which, together with industrial fishing, is causing collapse of key species populations within these ecosystems. Industrial pollution and burning hydrocarbons is causing polar warming which threatens to destabilize the remaining ice-sheets and reservoirs of methane stored in the polar oceans and permafrost. With populations in the US, China and India still rising, these clearly unsustainable practices are set to continue. The critical question is how long can planetary environmental processes continue to function before these human-induced changes trigger negative feedbacks that result in a switch to an alternate and less supportive Earth System state?

What are the spatial and temporal characteristics of natural climate variability?

The climate system exhibits internal variability on a broad range of timescales. However, the observational record is short, and the understanding of climate variability on decadal timescales and longer is therefore limited.

The detection and attribution of anthropogenic climate change requires a complete understanding of the spatial and temporal characteristics of natural climate variability. Furthermore, without such an understanding, we are not able to evaluate the ability of climate models to simulate past and present variability. This limits our confidence in the ability of the models to simulate future climate variability and change.

A critical focus of Earth system research over the coming decade should therefore be on combining observational and palaeoclimatic data to reconstruct natural climate variability over recent centuries and millennia.

What is the net effect of changing cloudiness on global climate?

The net effect of the present cloudiness is to clearly cool the global climate. Will the green house gas induced climate change strengthen or diminish the net effect of clouds on, e.g. surface temperature?

What are the feed back mechanisms between biodiversity and climate, how will they change over the next decades and what are the consequences?

Climate change and biodiversity change are interacting in feed-back loops that are poorly understood and unquantified and modelled. This applies to changing land (agriculture, desertification, cities, etc), and oceans (colour and physical stability of the ocean surface, acidification and calcifying organisms etc.) alike. The changing physico-chemical environment will exert important selective pressures on biological species and communities. Extinction of vulnerable species and explosions of adapted species are to be expected. They will change surface characteristics such as temperature, colour and albedo, gas exchange and atmospheric composition (CO2, NOx, methane). To predict the consequences a good understanding of these feed-back mechanisms is required, both on land and in the oceans.ue

In terms of livelihood risks and planning challenges, is rainfall variability more significant than climate change?

Rainfall patterns typically vary in a basin. This variability presents major risks to farmers’ livelihoods and challenges to planners to create proper structures for water storage and conveyance. With climate change, the frequency of extreme events is expected to increase and make the impacts of variability more pronounced. It is therefore important to clarify the significance of rainfall variability and suggest approaches to document and deal with the challenges involved.

How can we get past the debates between natural and anthropogenic causes of global changes, and shift our attention towards reducing and dealing with the impacts of these changes?

How to minimize the natural vs anthropogenic controversy on global changes/warming issues? It seems that there is no more scientific doubts that climate changes are moving the earth system to a warmer period. It seems that the actual controversy on how much is natural and how much is human related is a worthless discussion in many senses. We have to focus on how to diminish the impacts rather than finding which is the guilty mechanism or process. Whatever the solutions, they have to be implemented in the human dimension first.

What are the key regional drivers of future climate change?

Globally, greenhouse gas forcing is the key driver in policy-relevent climate change (ie. over the next 20, 50, 100 years). Regionally -at the scales people live, ecosystems function, water is obtained and crops grown, other forcings can dominate. Land cover change, urbanization, industrial aerosols etc can all have regional fingerprints that while globally small are locally dominant. Other modes of variability, ocean-atmopshere coupling, land-atmopshere coupling, orographic effects etc all can be locally dominant drivers even if they are lost in any global measure of climate change. A research program to understand drivers of climate change at the scales that people live is hugely challenging at a scientific level, technical level for the modelling and in terms of research at the interface of risk and vulnerability.