In the post-Paris political landscape, the relationship between science and politics is changing. We discuss what this means for the Intergovernmental Panel on Climate Change (IPCC), using recent controversies over negative emissions technologies (NETs) as a window into the fraught politics of producing policy-relevant pathways and scenarios. We suggest that pathways and scenarios have a ‘world-making’ power, potentially shaping the world in their own image and creating new political realities. Assessment bodies like the IPCC need to reflect on this power, and the implications of changing political contexts, in new ways.

The widespread retreat of mountain glaciers is a striking emblem of recent climate change. Yet mass-balance observations indicate that many glaciers are out of equilibrium with current climate, meaning that observed retreats do not show the full response to warming. This is a fundamental consequence of glacier dynamics: mountain glaciers typically have multidecadal response timescales, and so their response lags centennial-scale climate trends. A substantial difference between transient and equilibrium glacier length persists throughout the warming period; we refer to this length difference as ‘disequilibrium’. Forcing idealized glacier geometries with gradual warming shows that the glacier response timescale fundamentally governs the evolution of disequilibrium. Comparing a hierarchy of different glacier models suggests that accurate estimates of ice thickness and climatology, which control the timescale, are more important than higher order ice dynamics for capturing disequilibrium. Current glacier disequilibrium has previously been estimated for a selection of individual glaciers; our idealized modeling shows that sustained disequilibrium is a fundamental response of glacier dynamics, and is robust across a range of glacier geometries. This implies that many mountain glaciers are committed to additional, kilometer-scale retreats, even without further warming. Disequilibrium must also be addressed when calibrating glacier models used for climate reconstructions and projections of retreat in response to future warming.

Limiting dangerous climate change is widely believed to require negative emissions. This prospect has sparked concerns about whether negative emissions could be scaled up quickly enough, along with concerns about their likely ethical costs. Building upon scenario modelling, this paper examines ethical concerns with negative emissions via the comparison of three alternate climate futures. This paper shows that the severity of concerns depends upon implementation conditions, and especially the extent of deferred mitigation. Negative emissions can be a valuable means of limiting dangerous climate change, or an unjust gamble against the future.

Under the Paris Agreement, nations have committed to preventing dangerous global warming. Scenarios for achieving net-zero emissions in the second half of this century depend on land (forests and bioenergy) to remove carbon from the atmosphere. Modelled levels of land-based mitigation could reduce the availability of productive agricultural land, and encroach on natural land, with potentially significant social and environmental consequences. However, these issues are poorly recognized in the policy-uptake of modelled outputs. Understanding how science and policy interact to produce expectations about mitigation pathways allows us to consider the trade-offs inherent in relying on land for mitigation.

Biomass energy with carbon capture and storage (BECCS) is represented in many integrated assessment models as a keystone technology in delivering the Paris Agreement on climate change. This paper explores six key challenges in relation to large scale BECCS deployment and considers ways to address these challenges. Research needs to consider how BECCS fits in the context of other mitigation approaches, how it can be accommodated within existing policy drivers and goals, identify where it fits within the wider socioeconomic landscape, and ensure that genuine net negative emissions can be delivered on a global scale.

Technologies and practices to remove carbon from the atmosphere (‘negative emissions technologies’) will be challenging to scale-up. Efforts to incentivize or govern their scale-up globally risk failing if they miss the social challenges. This paper analyzes prospective challenges for negative emissions through examining how decarbonization practices are evolving in one particular landscape: the Imperial Valley in southeast California, a desert landscape engineered for industrial agriculture. Based on semi-structured interviews and site visits, this paper examines how community actors have received, participated in, imagined or contested new energy technologies and climate practices, and draws out takeaways for negative emissions policy.

The increasingly negative mass balance of the Greenland ice sheet (GrIS) over the last ~25 years has been associated with enhanced surface melt and increased ice loss from marine-terminating outlet glaciers. Accelerated retreat during 2000–2010 was concentrated in the southeast and northwest sectors of the ice sheet; however, there was considerable spatial and temporal variability in the timing and magnitude of retreat both within and between these regions. This behaviour has yet to be quantified and compared for all glaciers in both regions. Furthermore, it is unclear whether retreat has continued after 2010 in the northwest, and whether the documented slowdown in the southeast post-2005 has been sustained. Here, we compare spatial and temporal patterns of frontal change in the northwest and southeast GrIS, for the period 2000–2015. Our results show near-ubiquitous retreat of outlet glaciers across both regions for the study period; however, the timing and magnitude of inter-annual frontal position change is largely asynchronous. We also find that since 2010, there is continued terminus retreat in the northwest, which contrasts with considerable inter-annual variability in the southeast. Analysis of the role of glacier-specific factors demonstrates that fjord and bed geometry are important controls on the timing and magnitude of glacier retreat.

Most domestic environmental laws control the act of emitting pollutants into the environment. As a result, they do not apply squarely to negative emissions technologies (NETs) that remove ambient contaminants and do not emit pollutants themselves. As a result, current US environmental laws cannot readily govern a NET unless it has features that would typically allow regulation of a clean-up, such as ownership of the polluted resources, being at fault for polluting them or instituting projects to restore them. We should reinterpret such laws to focus on actual disruption or harm to the environment instead of using emission of pollutants as a proxy for ecological damage.

Simple models of glacier volume evolution are important in understanding features of glacier response to climate change, due to the scarcity of data adequate for running more complex models on a global scale. Two quantities of interest in a glacier's response to climate changes are its response time and its volume sensitivity to changes in the equilibrium line altitude (ELA). We derive a simplified, computationally inexpensive model of glacier volume evolution based on a block model with volume–area–length scaling. After analyzing its steady-state properties, we apply the model to each mountain glacier worldwide and estimate regionally differentiated response times and sensitivities to ELA changes. We use a statistical method from the family of global sensitivity analysis methods to determine the glacier quantities, geometric and climatic, that most influence the model output. The response time is dominated by the climatic setting reflected in the mass-balance gradient in the ablation zone, followed by the surface slope, while volume sensitivity is mainly affected by glacier size, followed by the surface slope.

With rapid and accelerated Arctic sea-ice loss, it is beneficial to update and baseline historical change on the regional scales from a consistent, intercalibrated, long-term time series of sea-ice data for understanding regional vulnerability and monitoring ice state for climate adaptation and risk mitigation. In this paper, monthly sea-ice extents (SIEs) derived from a passive microwave sea-ice concentration climate data record for the period of 1979–2015, are used to examine Arctic-wide and regional temporal variability of sea-ice cover and their decadal trends for 15 regions of the Arctic. Three unique types of SIE annual cycles are described. Regions of vulnerability within each of three types to further warming are identified. For the Arctic as a whole, the analysis has found significant changes in both annual SIE maximum and minimum, with −2.41 ± 0.56% per decade and −13.5 ± 2.93% per decade change relative to the 1979–2015 climate average, respectively. On the regional scale, the calculated trends for the annual SIE maximum range from +2.48 to −10.8% decade−1, while the trends for the annual SIE minimum range from 0 to up to −42% decade−1.

The Arctic marine environment is undergoing a transition from thick multi-year to first-year sea-ice cover with coincident lengthening of the melt season. Such changes are evident in the Baffin Bay-Davis Strait-Labrador Sea (BDL) region where melt onset has occurred ~8 days decade−1 earlier from 1979 to 2015. A series of anomalously early events has occurred since the mid-1990s, overlapping a period of increased upper-air ridging across Greenland and the northwestern North Atlantic. We investigate an extreme early melt event observed in spring 2013. (~6σ below the 1981–2010 melt climatology), with respect to preceding sub-seasonal mid-tropospheric circulation conditions as described by a daily Greenland Blocking Index (GBI). The 40-days prior to the 2013 BDL melt onset are characterized by a persistent, strong 500 hPa anticyclone over the region (GBI >+1 on >75% of days). This circulation pattern advected warm air from northeastern Canada and the northwestern Atlantic poleward onto the thin, first-year sea ice and caused melt ~50 days earlier than normal. The episodic increase in the ridging atmospheric pattern near western Greenland as in 2013, exemplified by large positive GBI values, is an important recent process impacting the atmospheric circulation over a North Atlantic cryosphere undergoing accelerated regional climate change.

The sustainability movement has more influence over company and government climate change actions than any treaty, law or regulation could possibly have, and results in quicker, measurable actions.

The sustainability movement is alive and well, and will continue to grow despite the outcry over some countries backpedaling from the Paris Accord. When one stops to consider just how much action companies from around the world have taken toward sustainability one cannot help but be amazed that so much was done without treaties, laws and regulations to force compliance. The primary driver of action is peer pressure—that which is derived from the actions of industry, and not the actions of government. This movement, found under a company’s corporate social responsibility (CSR) banner, will continue to grow by virtue of the continuous adoption of sustainability reporting, and in particular, supply chain reporting, benchmarking and risk management practices of industry, and the adoption of energy efficient (EE) projects. These actions have already resulted in significant positive changes to private company and government behavior, company value, lower emissions, greater operational efficiency, and competitive advantage. One could argue that peer pressure is much more effective than any treaty, laws, or regulations could possibly be. But, it should be noted that the term “climate change” remains a contentious issue and companies would be wise to refer to all related actions as sustainability.

This article compiles and categorizes the various forms of climate risk facing the fossil fuel industry. The type and intensity of risk differs greatly among the three forms of fossil fuels, as well as between countries in the developing and developed world. The paper finds heightened risk for the coal industry and reduced risk for oil businesses, due to its lack of substitutes.

Burning coal, oil, and natural gas is the source of two-thirds of the world’s emissions of greenhouse gases. Sales of these fuels also represent the economic underpinning of resource-rich countries and the world’s largest firms. As such, steps taken to abate emissions undermine commercial opportunities to monetize fossil fuel reserves. Risks to the industry correlate with progress on climate goals.

This article analyzes recent literature on climate action strategy and finds that a new or intensified set of risks has arisen for the fossil fuel industry. These include government policies and legislation, financial restrictions among lenders and insurers, hostile legal and shareholder actions, changes in demand and geopolitics, as well as the onset of new competitive forces among states and technologies.

The exposure of carbon-based businesses to these risks and the potential for loss is neither distributed uniformly across the sector, nor adheres to a uniform time scale. Shareholder-owned firms in the developed world will be incentivized to react sooner than large state-owned resource owners in developing countries. The fates of the three fossil fuels also appear likely to play out differently. Demand for oil appears insulated by its lack of viable substitutes, while coal businesses are already undergoing climate-related action, pushed by decreasing social acceptance and constraining financial regulation. At the other end of the spectrum, climate action has improved the medium-term viability of low-carbon natural gas. What appears clear is that, as effects of climate change grow more pronounced, the industry faces a future that is less accepting of current practices.

This paper presents, through text and the design project ‘The Silt House’, an alternative architecture for flood landscapes.

The investigation sets out the context for current forms of infrastructure and architecture planned in response to the increased threat of flooding in and around the Thames Estuary. In particular, it looks to certain experimental flood defence systems, suggesting, that instead of building bigger and bigger sea walls, we should look to use the landscape as a hybrid landscape infrastructure where salt marshes can act as a storage point for excess water and the flora can dispel energy from flood tides. Within this context, the text and design work seek to address the questions: what formal and spatial logics might be appropriate for architecture if sited in such a hybridised landscape like the tidal marsh; and, how might these logics mirror the particular conditions of this new model of infrastructure?

To help answer this question, the work looks to the architect and poet Raimund Abraham and, in particular, his 10 Houses projects developed between 1970 and 1973 for an alternative architectural model that uses natural processes to create enclosure and define architectural space. The design project seeks to explore how the direct use of such a historical reference can itself be seen as a means to not only develop an architecture that demonstrates a symbiotic relationship between nature and architecture, but also between the social and the political.

We develop a process-based model for the dispersion of a passive scalar in the turbulent flow around the buildings of a city centre. The street network model is based on dividing the airspace of the streets and intersections into boxes, within which the turbulence renders the air well mixed. Mean flow advection through the network of street and intersection boxes then mediates further lateral dispersion. At the same time turbulent mixing in the vertical detrains scalar from the streets and intersections into the turbulent boundary layer above the buildings. When the geometry is regular, the street network model has an analytical solution that describes the variation in concentration in a near-field downwind of a single source, where the majority of scalar lies below roof level. The power of the analytical solution is that it demonstrates how the concentration is determined by only three parameters. The plume direction parameter describes the branching of scalar at the street intersections and hence determines the direction of the plume centreline, which may be very different from the above-roof wind direction. The transmission parameter determines the distance travelled before the majority of scalar is detrained into the atmospheric boundary layer above roof level and conventional atmospheric turbulence takes over as the dominant mixing process. Finally, a normalised source strength multiplies this pattern of concentration. This analytical solution converges to a Gaussian plume after a large number of intersections have been traversed, providing theoretical justification for previous studies that have developed empirical fits to Gaussian plume models. The analytical solution is shown to compare well with very high-resolution simulations and with wind tunnel experiments, although re-entrainment of scalar previously detrained into the boundary layer above roofs, which is not accounted for in the analytical solution, is shown to become an important process further downwind from the source.

Addressing the challenge of ecological limits to economic growth and protection of the commons has been the central focus of scholarly research and policy debate in the world of EDE over the past two decades. Notable progress has been realized on a number of fronts but big challenges remain. Advances in the theory and practice of sustainable development, moving away from income measures such as GDP and promoting inclusive wealth as the right indicator of change in wellbeing and sustainability for the evaluation of economic performance and associated progress with the development and use of natural resources and environmental accounts represent one major example. Another important example is the ecosystem services (ES) approach of the millennium ecosystem assessment that has now become the main framework widely adopted as the basis for the characterization, valuation and evaluation of tradeoffs among the multiple services of ecosystems impacted by the pursuit of economic growth. Together with progress in the science and economics of addressing climate change, these advances moved the EDE focus from micro- to macro-environmental economics management issues. Major manifestations of progress on these fronts include: the emphasis on the green economy for ‘the future we want’ at Rio+20 and the intended move beyond the millennium development goals (MDGs) to redirect future efforts of the international community towards new sustainable development goals (SDGs) and targets; global consensus and support for establishing an Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES); and efforts to better define planetary boundaries.

The competition between wind and buoyancy forces acting on a naturally ventilated building with one upwind and one downwind opening and a distributed heat source can lead to multiple steady states. This study considers the impact of a second downwind opening on the existence of these multiple steady states. It is found that if this new opening exceeds a critical area, then the multiple steady states are eliminated, and the transition from buoyancy to wind dominated flow is continuous. This critical area is shown to be a function of the relative heights of the three windows. The predictions of the model are in accord with new laboratory experiments, and the implications for building design are discussed.