Abstract An analysis of 1168 modern soil profiles from the US Natural Resources Conservation Serv... more Abstract An analysis of 1168 modern soil profiles from the US Natural Resources Conservation Service yields no correlation between mean annual precipitation and depth to the top of the carbonate horizon (r 2= 0.03; p< 0.001). Parent material and soil texture both play negligible roles in this regression. When combined with similar published studies (n= 1481), r 2 improves slightly (r 2= 0.31; p< 0.001). Caution is therefore advised in using this or any previously published regression for inferring paleoprecipitation from paleosols. ...
The evolution of Earth's climate on geological timescales is largely driven by variations in ... more The evolution of Earth's climate on geological timescales is largely driven by variations in the magnitude of total solar irradiance (TSI) and changes in the greenhouse gas content of the atmosphere. Here we show that the slow ∼50 Wm(-2) increase in TSI over the last ∼420 million years (an increase of ∼9 Wm(-2) of radiative forcing) was almost completely negated by a long-term decline in atmospheric CO2. This was likely due to the silicate weathering-negative feedback and the expansion of land plants that together ensured Earth's long-term habitability. Humanity's fossil-fuel use, if unabated, risks taking us, by the middle of the twenty-first century, to values of CO2 not seen since the early Eocene (50 million years ago). If CO2 continues to rise further into the twenty-third century, then the associated large increase in radiative forcing, and how the Earth system would respond, would likely be without geological precedent in the last half a billion years.
... The leaf on the slow-return end of the spectrum (left side) is modern Hakea dactyloides (Prot... more ... The leaf on the slow-return end of the spectrum (left side) is modern Hakea dactyloides (Proteaceae), collected near Sydney, New South Wales, Australia. ... (2007) applied this method to two well-known fossil floras: Republic (Washington, USA; 49 Ma) and Bonanza (Utah, USA ...
Most modern C3 seed plants show an inverse relationship between PCO2 and stomatal index (SI), whe... more Most modern C3 seed plants show an inverse relationship between PCO2 and stomatal index (SI), where SI is the proportion of epidermal cells that are stomatal packages. This plant-atmosphere response therefore provides a reliable approach for estimating paleo-CO2 levels. Since stomatal responses to CO2 are generally species-specific, one is limited in paleo-reconstructions to species that exist both in the fossil record and living today. Fossils morphologically similar to living Ginkgo biloba and Metasequoia glyptostroboides extend back to the early and late Cretaceous, respectively, indicating that the fossil and living forms are very closely related. Measurements of SI made on fossil Ginkgo and Metasequoia were calibrated with historical collections of G. biloba and M. glyptostroboides leaves from sites that developed during the anthropogenically-driven CO2 increases of the past 145 years (288-369 ppmv) and with saplings of G. biloba and M. glyptostroboides grown in CO2 controlled growth chambers (350-800 ppmv). Both nonlinear regressions are highly significant (Ginkgo: n = 40, r2 = 0.91; Metasequoia: n = 18; r2 = 0.85). Results from a sequence of 23 latest Cretaceous to early Eocene-aged Ginkgo-bearing sites indicate that CO2 remained between 300 and 450 ppmv with the exception of one high estimate ( ~800 ppmv) near the Paleocene/Eocene boundary, and results from 4 middle Miocene-aged Ginkgo- and Metasequoia-bearing sites indicate that CO2 was between 320 and 400 ppmv. If correct, the CO2 values estimated here are too low to explain via the CO2 greenhouse effect alone the higher global mean temperatures (e.g., 3-4 ° C for the early Eocene) inferred from models and geological data for these two intervals.
Proceedings of the Royal Society B: Biological Sciences, 2013
Models generally predict a response in species richness to climate, but strong climate-diversity ... more Models generally predict a response in species richness to climate, but strong climate-diversity associations are seldom observed in long-term (more than 10(6) years) fossil records. Moreover, fossil studies rarely distinguish between the effects of atmospheric CO2 and temperature, which limits their ability to identify the causal controls on biodiversity. Plants are excellent organisms for testing climate-diversity hypotheses owing to their strong sensitivity to CO2, temperature and moisture. We find that pollen morphospecies richness in an angiosperm-dominated record from the Palaeogene and early Neogene (65-20 Ma) of Colombia and Venezuela correlates positively to CO2 much more strongly than to temperature (both tropical sea surface temperatures and estimates of global mean surface temperature). The weaker sensitivity to temperature may be due to reduced variance in long-term climate relative to in higher latitudes, or to the occurrence of lethal or sub-lethal temperatures during the warmest times of the Eocene. Physiological models predict that productivity should be the most sensitive to CO2 within the angiosperms, a prediction supported by our analyses if productivity is linked to species richness; however, evaluations of non-angiosperm assemblages are needed to more completely test this idea.
... The leaf on the slow-return end of the spectrum (left side) is modern Hakea dactyloides (Prot... more ... The leaf on the slow-return end of the spectrum (left side) is modern Hakea dactyloides (Proteaceae), collected near Sydney, New South Wales, Australia. ... (2007) applied this method to two well-known fossil floras: Republic (Washington, USA; 49 Ma) and Bonanza (Utah, USA ...
Abstract An analysis of 1168 modern soil profiles from the US Natural Resources Conservation Serv... more Abstract An analysis of 1168 modern soil profiles from the US Natural Resources Conservation Service yields no correlation between mean annual precipitation and depth to the top of the carbonate horizon (r 2= 0.03; p< 0.001). Parent material and soil texture both play negligible roles in this regression. When combined with similar published studies (n= 1481), r 2 improves slightly (r 2= 0.31; p< 0.001). Caution is therefore advised in using this or any previously published regression for inferring paleoprecipitation from paleosols. ...
The evolution of Earth's climate on geological timescales is largely driven by variations in ... more The evolution of Earth's climate on geological timescales is largely driven by variations in the magnitude of total solar irradiance (TSI) and changes in the greenhouse gas content of the atmosphere. Here we show that the slow ∼50 Wm(-2) increase in TSI over the last ∼420 million years (an increase of ∼9 Wm(-2) of radiative forcing) was almost completely negated by a long-term decline in atmospheric CO2. This was likely due to the silicate weathering-negative feedback and the expansion of land plants that together ensured Earth's long-term habitability. Humanity's fossil-fuel use, if unabated, risks taking us, by the middle of the twenty-first century, to values of CO2 not seen since the early Eocene (50 million years ago). If CO2 continues to rise further into the twenty-third century, then the associated large increase in radiative forcing, and how the Earth system would respond, would likely be without geological precedent in the last half a billion years.
... The leaf on the slow-return end of the spectrum (left side) is modern Hakea dactyloides (Prot... more ... The leaf on the slow-return end of the spectrum (left side) is modern Hakea dactyloides (Proteaceae), collected near Sydney, New South Wales, Australia. ... (2007) applied this method to two well-known fossil floras: Republic (Washington, USA; 49 Ma) and Bonanza (Utah, USA ...
Most modern C3 seed plants show an inverse relationship between PCO2 and stomatal index (SI), whe... more Most modern C3 seed plants show an inverse relationship between PCO2 and stomatal index (SI), where SI is the proportion of epidermal cells that are stomatal packages. This plant-atmosphere response therefore provides a reliable approach for estimating paleo-CO2 levels. Since stomatal responses to CO2 are generally species-specific, one is limited in paleo-reconstructions to species that exist both in the fossil record and living today. Fossils morphologically similar to living Ginkgo biloba and Metasequoia glyptostroboides extend back to the early and late Cretaceous, respectively, indicating that the fossil and living forms are very closely related. Measurements of SI made on fossil Ginkgo and Metasequoia were calibrated with historical collections of G. biloba and M. glyptostroboides leaves from sites that developed during the anthropogenically-driven CO2 increases of the past 145 years (288-369 ppmv) and with saplings of G. biloba and M. glyptostroboides grown in CO2 controlled growth chambers (350-800 ppmv). Both nonlinear regressions are highly significant (Ginkgo: n = 40, r2 = 0.91; Metasequoia: n = 18; r2 = 0.85). Results from a sequence of 23 latest Cretaceous to early Eocene-aged Ginkgo-bearing sites indicate that CO2 remained between 300 and 450 ppmv with the exception of one high estimate ( ~800 ppmv) near the Paleocene/Eocene boundary, and results from 4 middle Miocene-aged Ginkgo- and Metasequoia-bearing sites indicate that CO2 was between 320 and 400 ppmv. If correct, the CO2 values estimated here are too low to explain via the CO2 greenhouse effect alone the higher global mean temperatures (e.g., 3-4 ° C for the early Eocene) inferred from models and geological data for these two intervals.
Proceedings of the Royal Society B: Biological Sciences, 2013
Models generally predict a response in species richness to climate, but strong climate-diversity ... more Models generally predict a response in species richness to climate, but strong climate-diversity associations are seldom observed in long-term (more than 10(6) years) fossil records. Moreover, fossil studies rarely distinguish between the effects of atmospheric CO2 and temperature, which limits their ability to identify the causal controls on biodiversity. Plants are excellent organisms for testing climate-diversity hypotheses owing to their strong sensitivity to CO2, temperature and moisture. We find that pollen morphospecies richness in an angiosperm-dominated record from the Palaeogene and early Neogene (65-20 Ma) of Colombia and Venezuela correlates positively to CO2 much more strongly than to temperature (both tropical sea surface temperatures and estimates of global mean surface temperature). The weaker sensitivity to temperature may be due to reduced variance in long-term climate relative to in higher latitudes, or to the occurrence of lethal or sub-lethal temperatures during the warmest times of the Eocene. Physiological models predict that productivity should be the most sensitive to CO2 within the angiosperms, a prediction supported by our analyses if productivity is linked to species richness; however, evaluations of non-angiosperm assemblages are needed to more completely test this idea.
... The leaf on the slow-return end of the spectrum (left side) is modern Hakea dactyloides (Prot... more ... The leaf on the slow-return end of the spectrum (left side) is modern Hakea dactyloides (Proteaceae), collected near Sydney, New South Wales, Australia. ... (2007) applied this method to two well-known fossil floras: Republic (Washington, USA; 49 Ma) and Bonanza (Utah, USA ...
Uploads
Papers by Dana Royer