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Project summary, description or abstract: This dataset contains model estimates of how Americans perceive the health risks of extreme heat events at the state, county, and census tract level in the U.S. Estimates are produced using a statistical model based on national survey data. These data are associated with the following publication: Howe, Peter D., Jennifer R. Marlon, Xinran Wang, and Anthony Leiserowitz. “Public perceptions of the health risks of extreme heat across U.S. states, counties, and neighborhoods.” 2019. Proceedings of the National Academy of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.1813145116

This dataset contains survey data of the U.S. adult population that includes self-reported heat-health symptoms, protective behaviors implemented during heat waves, and perceptions of how a heat wave would affect personal health and the health of others. Temperature estimates of what participants may have experienced the summer prior to the survey are included at the county level. Demographic variables and spatial scales by region, state, and county are also included.

In the version of this Review Article originally published, ref. 10 was mistakenly cited instead of ref. 107 at the end of the sentence: “This complexity of residual ice cover makes it likely that HTM warming was regional, rather than global, and its peak warmth thus had different timing in different locations.” In addition, for ref. 108, Scientific Reports was incorrectly given as the publication name; it should have been Scientific Data. These errors have now been corrected in the online versions.

The location, timing, spatial extent, and frequency of wildfires are changing rapidly in many parts of the world, producing substantial impacts on ecosystems, people, and potentially climate. Paleofire records based on charcoal accumulation in sediments enable modern changes in biomass burning to be considered in their long-term context. Paleofire records also provide insights into the causes and impacts of past wildfires and emissions when analyzed in conjunction with other paleoenvironmental data and with fire models. Here we present new 1000-year and 22 000-year trends and gridded biomass burning reconstructions based on the Global Charcoal Database version 3 (GCDv3), which includes 736 charcoal records (57 more than in version 2). The new gridded reconstructions reveal the spatial patterns underlying the temporal trends in the data, allowing insights into likely controls on biomass burning at regional to global scales. In the most recent few decades, biomass burning has sharply increased in both hemispheres but especially in the north, where charcoal fluxes are now higher than at any other time during the past 22 000 years. We also discuss methodological issues relevant to data–model comparisons and identify areas for future research. Spatially gridded versions of the global data set from GCDv3 are provided to facilitate comparison with and validation of global fire simulations.

Ongoing changes in disturbance regimes are predicted to cause acute changes in ecosystem structure and function in the coming decades, but many aspects of these predictions are uncertain. A key challenge is to improve the predictability of postdisturbance biogeochemical trajectories at the ecosystem level. Ecosystem ecologists and paleoecologists have generated complementary data sets about disturbance (type, severity, frequency) and ecosystem response (net primary productivity, nutrient cycling) spanning decadal to millennial timescales. Here, we take the first steps toward a full integration of these data sets by reviewing how disturbances are reconstructed using dendrochronological and sedimentary archives and by summarizing the conceptual frameworks for carbon, nitrogen, and hydrologic responses to disturbances. Key research priorities include further development of paleoecological techniques that reconstruct both disturbances and terrestrial ecosystem dynamics. In addition, mechanistic detail from disturbance experiments, long-term observations, and chronosequences can help increase the understanding of ecosystem resilience.

Over the past 3.5 million years, there have been several intervals when climate conditions were warmer than during the pre-industrial Holocene. Although past intervals of warming were forced differently than future anthropogenic change, such periods can provide insights into potential future climate impacts and ecosystem feedbacks, especially over centennial-to-millennial timescales that are often not covered by climate model simulations. Our observation-based synthesis of the understanding of past intervals with temperatures within the range of projected future warming suggests that there is a low risk of runaway greenhouse gas feedbacks for global warming of no more than 2 °C. However, substantial regional environmental impacts can occur. A global average warming of 1–2 °C with strong polar amplification has, in the past, been accompanied by significant shifts in climate zones and the spatial distribution of land and ocean ecosystems. Sustained warming at this level has also led to substantial reductions of the Greenland and Antarctic ice sheets, with sea-level increases of at least several metres on millennial timescales. Comparison of palaeo observations with climate model results suggests that, due to the lack of certain feedback processes, model-based climate projections may underestimate long-term warming in response to future radiative forcing by as much as a factor of two, and thus may also underestimate centennial-to-millennial-scale sea-level rise.

The Earth has experienced large changes in global and regional climates over the past one million years. Understanding processes and feedbacks that control those past environmental changes is of great interest for better understanding the nature, direction and magnitude of current climate change, its effect on life, and on the physical, biological and chemical processes and ecosystem services important for human well-being. Microfossils from terrestrial plants – pollen, microcharcoal and phytoliths – preserved in terrestrial and marine sedimentary archives are particularly useful tools to document changes in vegetation, fire and land climate. They are well-preserved in a variety of depositional environments and provide quantitative reconstructions of past land cover and climate. Those microfossil data are widely available from public archives, and their spatial coverage includes almost all regions on Earth, including both high and low latitudes and altitudes. Here, we (i) review the laboratory procedures used to extract those microfossils from sediment for microscopic observations and the qualitative and quantitative information they provide, (ii) highlight the importance of regional and global databases for large-scale syntheses of environmental changes, and (iii) review the application of terrestrial plant microfossil records in palaeoclimatology and palaeoecology using key examples from specific regions and past periods.