David Armstrong McKay

University of Exeter | UoE · Global Systems Institute

Agricultural intensification has significantly increased yields and fed growing populations across the planet, but has also led to considerable environmental degradation. In response an alternative process of ‘Sustainable Intensification’ (SI), whereby food production increases while environmental impacts are reduced, has been advocated as necessar...

Several past episodes of rapid carbon cycle and climate change are hypothesised to be the result of the Earth system reaching a tipping point beyond which an abrupt transition to a new state occurs. At the Palaeocene–Eocene Thermal Maximum (PETM) at ∼ 56 Ma and at subsequent hyperthermal events, hypothesised tipping points involve the abrupt transf...

Some ecosystems undergo abrupt transitions to a new regime after passing a tipping point in an exogenous stressor, for example lakes shifting from a clear to turbid ‘eutrophic’ state in response to nutrient-enrichment. Metrics-based resilience indicators have been developed as early warning signals of these shifts but have not always proved reliabl...

The Earth's oceans are one of the largest sinks in the Earth system for anthropogenic CO2 emissions, acting as a negative feedback on climate change. Earth system models project that climate change will lead to a weakening ocean carbon uptake rate as warm water holds less dissolved CO2 and as biological productivity declines. However, most Earth sy...

Climate tipping points occur when change in a part of the climate system becomes self-perpetuating beyond a warming threshold, leading to substantial Earth system impacts. Synthesizing paleoclimate, observational, and model-based studies, we provide a revised shortlist of global "core" tipping elements and regional "impact" tipping elements and the...

Tipping points characterize the situation when a system experiences abrupt, rapid and sometimes irreversible changes. Given that such changes are in most cases undesirable, numerous approaches have been proposed to identify if a system is close to a tipping point. Such approaches have been termed early-warning signals and represent a set of methods...

The stability and resilience of the Earth system and human well-being are inseparably linked1–3, yet their interdependencies are generally under-recognized; consequently, they are often treated independently4,5. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, wate...

Safe and just Earth System Boundaries (ESBs) for surface and groundwater (blue water) have been defined for sustainable water management in the Anthropocene. We evaluate where minimum human needs can be met within the surface water ESB and, where this is not possible, identify how much groundwater is required. 2.6 billion people live in catchments...

Current policies and actions make it very likely, at least temporarily, to overshoot the Paris climate targets of 1.5–<2.0 °C above pre-industrial levels. If this global warming range is exceeded, potential tipping elements such as the Greenland Ice Sheet and Amazon rainforest may be at increasing risk of crossing critical thresholds. This raises t...

The Sustainable Development Goals aim to improve access to resources and services, reduce environmental degradation, eradicate poverty and reduce inequality. However, the magnitude of the environmental burden that would arise from meeting the needs of the poorest is under debate—especially when compared to much larger burdens from the rich. We show...

We are in a climate and ecological emergency, where climate change and direct anthropogenic interference with the biosphere are risking abrupt and/or irreversible changes that threaten our life-support systems. Efforts are underway to increase the resilience of some ecosystems that are under threat, yet collective awareness and action are modest at...

The UN 2030 Agenda includes 17 Sustainable Development Goals towards improving access to resources and services, reducing environmental degradation and bringing down inequality. However, there is debate on the magnitude of the environmental burden that would arise from meeting the needs of the poorest, especially compared to much larger burdens fro...

Climate tipping elements play a crucial role for the stability of the Earth system under human pressures and are potentially at risk of disintegrating within and partially even below the Paris temperature guardrails of 1.5-2.0°C above pre-industrial levels. However, current policies and actions make it very likely to, at least temporarily, transgre...

The Swedish Varve Chronology is an unparalleled tool for linking the deglacial history of Sweden with associated palaeo‐environmental change at an annual time scale, and it forms part of Sweden's cultural heritage. A full deglacial chronology connected to the present day does not yet exist; a notable gap is in southeasternmost Sweden, where few var...

Varve thickness data from legacy and newly-acquired annually-laminated sediment archives in varve years on the local Skåne-Småland timescale, along with the details of the sediment sites. Here we have reanalysed legacy data and incorporated our own new terrestrial and offshore data to create a new chronology, the Skåne-Småland varve chronology. Usi...

The Earth’s oceans are one of the largest sinks in the Earth system for anthropogenic CO2 emissions, acting as a negative feedback on climate change. Earth system models predict, though, that climate change will lead to a weakening ocean carbon uptake rate as warm water holds less dissolved CO2 and biological productivity declines. However, most Ea...

Over the past 15 years climate tipping points have emerged as both an important research topic and source of public concern. Some articles have suggested that some tipping points could begin within the 1.5-2oC Paris climate target range, with many more potentially starting by the ~3-4oC of warming that current policy is projected to be committed to...

We explore the evolutionary nature of interactions between government policy, farm decision-making and ecosystem services in Shucheng County, Anhui Province, 1950–2015. Analyses of ecological, social and economic trends are complemented by interviews with local farmers. Since the Household Responsibility System started in 1980, there has been a tra...

Several past episodes of rapid carbon cycle and climate change are hypothesised to be the result of the Earth system reaching a tipping point beyond which an abrupt transition to a new state occurs. At the Palaeocene-Eocene Thermal Maximum (PETM) ~ 56 Ma, and at subsequent hyperthermal events, hypothesised tipping points involve the abrupt transfer...

During the Paleocene-Eocene Thermal Maximum (PETM), the carbon isotopic signature (δ13C) of surface carbon-bearing phases decreased abruptly by at least 2.5 to 3.0 ‰. This carbon isotope excursion (CIE) has been attributed to widespread methane hydrate dissociation in response to rapid ocean warming. We ran a thermohydraulic modeling code to simula...

The Eocene-Oligocene Transition (EOT), ~34 million years ago, marks a tipping point in the long-term Cenozoic greenhouse to icehouse climate transition. Paleorecords reveal stepwise rapid cooling and ice growth across the EOT tightly coupled to a transient benthic δ13C excursion and a major and permanent deepening of the carbonate compensation dept...

Over the course of the Cenozoic the Earth system has shifted from a CO2-rich ‘Greenhouse’ climate state to a CO2-poor ‘Icehouse’ climate state. This trend is punctuated by numerous perturbations to the carbon-climate system, but the extent of the coupling between the carbon cycle and climate system, the drivers of these perturbations, and their rel...

Significance Ammonites went extinct at the time of the end-Cretaceous asteroid impact, as did more than 90% of species of calcium carbonate-shelled plankton (coccolithophores and foraminifera). Comparable groups not possessing calcium carbonate shells were less severely affected, raising the possibility that ocean acidification, as a side effect of...

Large Igneous Provinces (LIPs) have been emplaced throughout Earth's history, erupting great quantities (>104 km3>104 km3) of lava in long-lived (>105 y>105 y) events that have been linked to major environmental disruptions. The largest LIP eruptions (e.g. Siberian Traps) are widely considered to have had an impact on global climate through basalt...

During the late Palaeogene the Earth’s climate shifted from a ‘Greenhouse’ to ‘Icehouse’ state, with a major episode of Antarctic glaciation and global cooling occurring at the Eocene-Oligocene Transition (EOT) ~34 million years ago. As illustrated in Figure 1, palaeorecords indicate that during the late Eocene global temperatures were high enough...

Large Igneous Provinces (LIPs) can result in significant degassing of mantle-derived CO2 into the ocean-atmosphere system, but only the largest LIPs are considered to have had a significant impact on global climate. However, some smaller LIPs also coincide with times of global warmth and carbon cycle perturbations. Here we use biogeochemical box mo...