Increased concentrations of atmospheric greenhouse gases have led to a global mean surface temperature 1.0°C higher than during the pre-industrial period. We expand on the recent IPCC Special Report on global warming of 1.5°C and review the additional risks associated with higher levels of warming, each having major implications for multiple geographies, climates, and ecosystems. Limiting warming to 1.5°C rather than 2.0°C would be required to maintain substantial proportions of ecosystems and would have clear benefits for human health and economies. These conclusions are relevant for people everywhere, particularly in low- and middle-income countries, where the escalation of climate-related risks may prevent the achievement of the United Nations Sustainable Development Goals.

A systematic global stocktake of evidence on human adaptation to climate changeAssessing global progress on human adaptation to climate change is an urgent priority. Although the literature on adaptation to climate change is rapidly expanding, little is known about the actual extent of implementation. We systematically screened >48,000 articles using machine learning methods and a global network of 126 researchers. Our synthesis of the resulting 1,682 articles presents a systematic and comprehensive global stocktake of implemented human adaptation to climate change. Documented adaptations were largely fragmented, local and incremental, with limited evidence of transformational adaptation and negligible evidence of risk reduction outcomes. We identify eight priorities for global adaptation research: assess the effectiveness of adaptation responses, enhance the understanding of limits to adaptation, enable individuals and civil society to adapt, include missing places, scholars and scholarship, understand private sector responses, improve methods for synthesizing different forms of evidence, assess the adaptation at different temperature thresholds, and improve the inclusion of timescale and the dynamics of responses.

Despite their heterogeneity, small island developing states (SIDS) are recognized as being particularly at risk to climate change, and, as they share numerous common traits, the United Nations recognizes them as a special group. SIDS have been quite vocal in calling attention to the challenges they face from climate change and advocating for greater international ambition to limit global warming. Here, we unpack factors that are helpful in understanding the relationship between climate change and SIDS through a review of studies that span disciplines and methodologies. We assess patterns of hazards, exposure, and vulnerability; impacts and risks; awareness and knowledge; adaptation planning and implementation; mitigation; loss and damage; and climate justice to provide an overarching review of literature on climate change and SIDS. Expected final online publication date for the Annual Review of Environment and Resources, Volume 45 is October 19, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.