About

Daniel P. Schrag is the Sturgis Hooper Professor of Geology and Professor of Environmental Science and Engineering at Harvard University. He also serves as Co-Director of the Science, Technology and Public Policy Program at the Harvard Kennedy School. His primary teaching areas include Environmental Science & Engineering. His research focuses on environmental science and engineering, biogeochemical cycles, climate change, climate dynamics, energy resources and energy systems, oceanography, solar geoengineering, and science, technology, innovation, and public policy. His work integrates scientific research with policy considerations to address pressing environmental challenges.

Research topics

• Paleontology
• Chemistry
• Geology
• Geochemistry
• Oceanography

Selected publications

• Carbon tax assets for carbon tax liabilities: using CBAM to increase climate finance

  Climate Policy · 2025-08-04 · 2 citations

  articleSenior author
  PublisherDOI

• Global mean sea level over the past 4.5 million years

  Science · 2025-10-16 · 19 citations

  articleOpen access

  Changes in global mean sea level (GMSL) during the late Cenozoic remain uncertain. We use a reconstruction of changes in δ 18 O of seawater to reconstruct GMSL since 4.5 million years ago (Ma) that accounts for temperature-driven changes in the δ 18 O of global ice sheets. Between 4.5 and 3 Ma, sea level highstands remained up to 20 m above present whereas the first lowstands below present suggest onset of Northern Hemisphere glaciation at 4 Ma. Intensification of global glaciation occurred from 3 Ma to 2.5 Ma, culminating in lowstands similar to the Last Glacial Maximum lowstand at 21,000 years ago and that reoccurred throughout much of the Pleistocene. We attribute the middle Pleistocene transition in ice sheet variability (1.2 Ma to 0.62 Ma) to modulation of 41-thousand-year (kyr) obliquity forcing by an increase in ~100-kyr CO 2 variability.

  PublisherOA PDFDOI

• Decarbonizing residential space heating with heat pumps in the United States

  Energy Policy · 2025-12-10 · 1 citations

  articleSenior author
  PublisherDOI

• Mean ocean temperature change and decomposition of the benthic <i>δ</i> ¹⁸ O record over the past 4.5 million years

  Climate of the past · 2025-06-03 · 6 citations

  articleOpen accessSenior authorCorresponding

  Abstract. We use a recent reconstruction of global mean sea surface temperature change relative to preindustrial (ΔGMSST) over the last 4.5 Myr together with independent proxy-based reconstructions of bottom water (ΔBWT) or deep-ocean (ΔDOT) temperatures to infer changes in mean ocean temperature (ΔMOT). Three independent lines of evidence show that the ratio of ΔMOT / ΔGMSST​​​​​​​, which is a measure of ocean heat storage efficiency (HSE), increased from ∼ 0.5 to ∼ 1 during the Middle Pleistocene Transition (MPT, 1.5–0.9 Ma), indicating an increase in ocean heat uptake (OHU) at this time. The first line of evidence comes from global climate models; the second from proxy-based reconstructions of ΔBWT, ΔMOT, and ΔGMSST; and the third from decomposing a global mean benthic δ18O stack (δ18Ob) into its temperature (δ18OT) and seawater (δ18Osw) components. Regarding the latter, we also find that further corrections in benthic δ18O, probably due to some combination of a long-term diagenetic overprint and to the carbonate ion effect, are necessary to explain reconstructed Pliocene sea-level highstands inferred from δ18Osw. We develop a simple conceptual model that invokes an increase in OHU and HSE during the MPT in response to changes in deep-ocean circulation driven largely by surface forcing of the Southern Ocean. Our model accounts for heat uptake and temperature in the non-polar upper ocean (0–2000 m) that is mainly due to wind-driven ventilation, while changes in the deeper ocean (&gt; 2000 m) in both polar and non-polar waters occur due to high-latitude deepwater formation. We propose that deepwater formation was substantially reduced prior to the MPT, effectively decreasing HSE. We attribute these changes in deepwater formation across the MPT to long-term cooling which caused a change starting ∼ 1.5 Ma from a highly stratified Southern Ocean due to warm SSTs and reduced sea-ice extent to a Southern Ocean which, due to colder SSTs and increased sea-ice extent, had a greater vertical exchange of water masses.

  PublisherOA PDFDOI

• Responding to rising heat in workplaces and homes of low income workers

  BMJ · 2025-11-04 · 3 citations

  articleOpen access
  PublisherOA PDFDOI

• Carbon abatement costs of green hydrogen across end-use sectors

  Joule · 2024-10-08 · 56 citations

  articleSenior author
  PublisherDOI

• A Revisionist View of the Mid-Pleistocene Transition

  2024-03-08

  preprintOpen access

  The Mid-Pleistocene Transition (MPT) is commonly characterized as a change in both temperature and ice volume from smaller amplitude, 41-kyr variability to higher amplitude, ~100-kyr variability in the absence of any significant change in orbital forcing. Here we reassess these characteristics based on our new reconstructions of changes in global mean surface temperature (DGMST) and global mean sea level over the last 2.5 Myr. Our reconstruction of DGMST includes an initial phase of long-term cooling through the early Pleistocene followed by a second phase of accelerated cooling during the MPT (1.5-0.9 Ma) that was accompanied by a transition from dominant 41-kyr low-amplitude periodicity to dominant ~100-kyr high-amplitude periodicity. Changes in rates of long-term cooling and variability are consistent with changes in the carbon cycle driven initially by geologic processes followed by additional changes during the MPT in the Southern Ocean carbon cycle. The spectrum of our sea-level reconstruction is dominated by 41-kyr variance until ~1.2 Ma with subsequent emergence of a ~100-kyr signal that, unlike global temperature, has nearly the same concentration of variance as the 41-kyr signal during this time. Moreover, our sea-level reconstruction is significantly different than all other reconstructions in showing fluctuations of large ice sheets throughout the Pleistocene as compared to a change from fluctuations in smaller to larger ice sheets during the MPT. We attribute their longer period variations after the MPT to modulation of obliquity forcing by the newly established low-frequency CO2 variability. Specifically, prior to reaching their maximum size at the end of each ~100-kyr interval, ice-sheet response to periods of lower CO2 was modulated by higher obliquity, and vice versa, with the times of maximum ice-sheet growth only occurring when low CO2 combined with the next obliquity low. Ice sheets then began to melt in response to the next increase in obliquity, with the subsequent sequence of events and feedbacks leading to a termination. High-resolution ice-core CO2 records that extend beyond 0.8 Ma are needed to test this hypothesis. Otherwise, large ice sheets shared a common size threshold throughout the Pleistocene equivalent to sea level below -80 m that, when exceeded, resulted in a termination that was paced by the next increase in obliquity.

  PublisherDOI

• A Faulty Foundation Supports a Powerful Idea: Mikhail Budyko and His Work on the Ice–Albedo Feedback

  SFI Press eBooks · 2024-01-01

  book-chapter1st authorCorresponding
  PublisherDOI

• Energy transition needs new materials

  Science · 2024-05-16 · 111 citations

  editorialOpen accessSenior author

  The decreasing cost of electricity worldwide from wind and solar energy, as well as that of end-use technologies such as electric vehicles, reflect substantial progress made toward replacing fossil fuels with alternative energy sources. But a full transition to clean energy can only be realized if numerous challenges are overcome. Many problems can be addressed through the discovery of new materials that improve the efficiency of energy production and consumption; reduce the need for scarce mineral resources; and support the production of green hydrogen, clean ammonia, and carbon-neutral hydrocarbon fuels. However, research and development of new energy materials are not as aggressive as they should be to meet the demands of climate change.

  PublisherOA PDFDOI

• Mean ocean temperature change and decomposition of the benthic δ ¹⁸ O record over the last 4.5 Myr

  2024-09-27 · 1 citations

  preprintOpen access

  Abstract. We use a recent compilation of global mean sea surface temperature changes (ΔGMSST) over the last 4.5 Myr together with independent proxy-based reconstructions of bottom water or deep ocean temperatures to infer changes in mean ocean temperature (ΔMOT). We find that the ratio of ΔMOT/ΔGMSST, which is also a measure of ocean heat storage efficiency, was around 0.5 before the Middle Pleistocene Transition (MPT, 1.5–0.9 Ma), but was 1 thereafter. This finding is also supported when using our ΔMOT to decompose a global mean benthic δ18O stack into its temperature and seawater components. However, further corrections in benthic δ18O, probably due to a long-term diagenetic overprint, are necessary to explain reconstructed Pliocene sea level highstands. Finally, we develop a theoretical understanding of why the ocean heat storage efficiency changed over the Plio-Pleistocene. According to our conceptual model, heat uptake and temperature in the non-polar upper ocean is mainly driven by wind, while changes in the deeper ocean in both polar and non-polar waters occur due to high-latitude deepwater formation. We propose that deepwater formation was substantially reduced prior to the MPT, effectively decreasing ΔMOT with respect to ΔGMSST. We attribute these changes in deepwater formation across the MPT to long-term cooling which caused a change starting ~1.5 Ma from a highly stratified Southern Ocean due to warm SSTs and reduced sea-ice extent to a Southern Ocean which, due to colder SSTs and increased sea-ice extent, had a greater vertical exchange of water masses.

  PublisherDOI

Recent grants

• Magnesium Isotope Geochemistry of Carbonate Sediments

  NSF · $300k · 2010–2013

• Oxygen Isotope Geochemistry of Marine Sulfate

  NSF · $301k · 2005–2008

Frequent coauthors

• Francis A. Macdonald

  83 shared

• Alexandra V. Turchyn

  University of Cambridge

  68 shared

• Michael N. Evans

  64 shared

• Andrew H. Knoll

  Harvard University

  58 shared

• David T. Johnston

  Planetary Science Institute

  57 shared

• Braddock K. Linsley

  Lamont-Doherty Earth Observatory

  48 shared

• Paul F. Hoffman

  University of Edinburgh

  45 shared

• John A. Higgins

  Princeton University

  44 shared