Andrew J. Watson

Bio: Andrew J. Watson is an academic researcher from University of Exeter. The author has contributed to research in topics: Blastocyst & Embryonic stem cell. The author has an hindex of 88, co-authored 497 publications receiving 34512 citations. Previous affiliations of Andrew J. Watson include Mansfield University of Pennsylvania & Plymouth Marine Laboratory.

Global Carbon Budget 2020

Abstract: Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2010–2019), EFOS was 9.6 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.4 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 1.6 ± 0.7 GtC yr−1. For the same decade, GATM was 5.1 ± 0.02 GtC yr−1 (2.4 ± 0.01 ppm yr−1), SOCEAN 2.5 ± 0.6 GtC yr−1, and SLAND 3.4 ± 0.9 GtC yr−1, with a budget imbalance BIM of −0.1 GtC yr−1 indicating a near balance between estimated sources and sinks over the last decade. For the year 2019 alone, the growth in EFOS was only about 0.1 % with fossil emissions increasing to 9.9 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.7 ± 0.5 GtC yr−1 when cement carbonation sink is included), and ELUC was 1.8 ± 0.7 GtC yr−1, for total anthropogenic CO2 emissions of 11.5 ± 0.9 GtC yr−1 (42.2 ± 3.3 GtCO2). Also for 2019, GATM was 5.4 ± 0.2 GtC yr−1 (2.5 ± 0.1 ppm yr−1), SOCEAN was 2.6 ± 0.6 GtC yr−1, and SLAND was 3.1 ± 1.2 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 409.85 ± 0.1 ppm averaged over 2019. Preliminary data for 2020, accounting for the COVID-19-induced changes in emissions, suggest a decrease in EFOS relative to 2019 of about −7 % (median estimate) based on individual estimates from four studies of −6 %, −7 %, −7 % (−3 % to −11 %), and −13 %. Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2019, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. Comparison of estimates from diverse approaches and observations shows (1) no consensus in the mean and trend in land-use change emissions over the last decade, (2) a persistent low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent discrepancy between the different methods for the ocean sink outside the tropics, particularly in the Southern Ocean. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Friedlingstein et al., 2019; Le Quere et al., 2018b, a, 2016, 2015b, a, 2014, 2013). The data presented in this work are available at https://doi.org/10.18160/gcp-2020 (Friedlingstein et al., 2020).

Climatological mean and decadal change in surface ocean pCO2, and net sea–air CO2 flux over the global oceans

Abstract: A climatological mean distribution for the surface water pCO2 over the global oceans in non-El Nino conditions has been constructed with spatial resolution of 4° (latitude) ×5° (longitude) for a reference year 2000 based upon about 3 million measurements of surface water pCO2 obtained from 1970 to 2007. The database used for this study is about 3 times larger than the 0.94 million used for our earlier paper [Takahashi et al., 2002. Global sea–air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects. Deep-Sea Res. II, 49, 1601–1622]. A time-trend analysis using deseasonalized surface water pCO2 data in portions of the North Atlantic, North and South Pacific and Southern Oceans (which cover about 27% of the global ocean areas) indicates that the surface water pCO2 over these oceanic areas has increased on average at a mean rate of 1.5 μatm y−1 with basin-specific rates varying between 1.2±0.5 and 2.1±0.4 μatm y−1. A global ocean database for a single reference year 2000 is assembled using this mean rate for correcting observations made in different years to the reference year. The observations made during El Nino periods in the equatorial Pacific and those made in coastal zones are excluded from the database. Seasonal changes in the surface water pCO2 and the sea-air pCO2 difference over four climatic zones in the Atlantic, Pacific, Indian and Southern Oceans are presented. Over the Southern Ocean seasonal ice zone, the seasonality is complex. Although it cannot be thoroughly documented due to the limited extent of observations, seasonal changes in pCO2 are approximated by using the data for under-ice waters during austral winter and those for the marginal ice and ice-free zones. The net air–sea CO2 flux is estimated using the sea–air pCO2 difference and the air–sea gas transfer rate that is parameterized as a function of (wind speed)2 with a scaling factor of 0.26. This is estimated by inverting the bomb 14C data using Ocean General Circulation models and the 1979–2005 NCEP-DOE AMIP-II Reanalysis (R-2) wind speed data. The equatorial Pacific (14°N–14°S) is the major source for atmospheric CO2, emitting about +0.48 Pg-C y−1, and the temperate oceans between 14° and 50° in the both hemispheres are the major sink zones with an uptake flux of −0.70 Pg-C y−1 for the northern and −1.05 Pg-C y−1 for the southern zone. The high-latitude North Atlantic, including the Nordic Seas and portion of the Arctic Sea, is the most intense CO2 sink area on the basis of per unit area, with a mean of −2.5 tons-C month−1 km−2. This is due to the combination of the low pCO2 in seawater and high gas exchange rates. In the ice-free zone of the Southern Ocean (50°–62°S), the mean annual flux is small (−0.06 Pg-C y−1) because of a cancellation of the summer uptake CO2 flux with the winter release of CO2 caused by deepwater upwelling. The annual mean for the contemporary net CO2 uptake flux over the global oceans is estimated to be −1.6±0.9 Pg-C y−1, which includes an undersampling correction to the direct estimate of −1.4±0.7 Pg-C y−1. Taking the pre-industrial steady-state ocean source of 0.4±0.2 Pg-C y−1 into account, the total ocean uptake flux including the anthropogenic CO2 is estimated to be −2.0±1.0 Pg-C y−1 in 2000.

A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization

Abstract: Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the 'iron hypothesis' For this reason, it is important to understand the response of pelagic biota to increased iron supply Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days This drawdown was mostly due to the proliferation of diatom stocks But downward export of biogenic carbon was not increased Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction

Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean

Abstract: The idea that iron might limit phytoplankton growth in large regions of the ocean has been tested by enriching an area of 64 km2 in the open equatorial Pacific Ocean with iron This resulted in a doubling of plant biomass, a threefold increase in chlorophyll and a fourfold increase in plant production Similar increases were found in a chlorophyll-rich plume down-stream of the Galapagos Islands, which was naturally enriched in iron These findings indicate that iron limitation can control rates of phytoplankton productivity and biomass in the ocean

In situ evaluation of air-sea gas exchange parameterizations using novel conservative and volatile tracers

Abstract: Measurements of air-sea gas exchange rates are reported from two deliberate tracer experiments in the southern North Sea during February 1992 and 1993. A conservative tracer, spores of the bacterium Bacillus globigii var. Niger, was used for the first time in an in situ air-sea gas exchange experiment. This nonvolatile tracer is used to correct for dispersive dilution of the volatile tracers and allows three estimations of the transfer velocity for the same time period. The first estimation of the power dependence of gas transfer on molecular diffusivity in the marine environment is reported. This allows the impact of bubbles on estimates of the transfer velocity derived from changes in the helium/sulphur hexafluoride ratio to be assessed. Data from earlier dual tracer experiments are reinterpreted, and findings suggest that results from all dual tracer experiments are mutually consistent. The complete data set is used to test published parameterizations of gas transfer with wind speed. A gas ex- change relationship that shows a dependence on wind speed intermediate between those ofLiss and Merlivat [1986] and Wanninkhof [1992] is found to be optimal. The dual tracer data are shown to be reasonably consistent with global estimates of gas exchange based on the uptake of natural and bomb-derived radiocarbon. The degree of scatter in the data when plotted against wind speed suggests that parameters not scaling with wind speed are also influencing gas exchange rates.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Planetary boundaries: Guiding human development on a changing planet

Abstract: The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.

Molecular characterization of a peripheral receptor for cannabinoids

Abstract: THE major active ingredient of marijuana, Δ9-tetrahydrocannabi-nol (Δ9-THC), has been used as a psychoactive agent for thousands of years. Marijuana, and Δ9-THC, also exert a wide range of other effects including analgesia, anti-inflammation, immunosuppression, anticonvulsion, alleviation of intraocular pressure in glaucoma, and attenuation of vomiting1. The clinical application of cannabinoids has, however, been limited by their psychoactive effects, and this has led to interest in the biochemical bases of their action. Progress stemmed initially from the synthesis of potent derivatives of δ9-THC4,5, and more recently from the cloning of a gene encoding a G-protein-coupled receptor for cannabinoids6. This receptor is expressed in the brain but not in the periphery, except for a low level in testes. It has been proposed that the non-psychoactive effects of cannabinoids are either mediated centrally or through direct interaction with other, non-receptor proteins1,7,8. Here we report the cloning of a receptor for cannabinoids that is not expressed in the brain but rather in macrophages in the marginal zone of spleen.

Nitrogen cycles: past, present, and future

Abstract: This paper contrasts the natural and anthropogenic controls on the conversion of unreactive N2 to more reactive forms of nitrogen (Nr). A variety of data sets are used to construct global N budgets for 1860 and the early 1990s and to make projections for the global N budget in 2050. Regional N budgets for Asia, North America, and other major regions for the early 1990s, as well as the marine N budget, are presented to highlight the dominant fluxes of nitrogen in each region. Important findings are that human activities increasingly dominate the N budget at the global and at most regional scales, the terrestrial and open ocean N budgets are essentially dis- connected, and the fixed forms of N are accumulating in most environmental reservoirs. The largest uncertainties in our understanding of the N budget at most scales are the rates of natural biological nitrogen fixation, the amount of Nr storage in most environmental reservoirs, and the production rates of N2 by denitrification.

Relationship between wind speed and gas exchange over the ocean

Abstract: Relationships between wind speed and gas transfer, combined with knowledge of the partial pressure difference of CO2 across the air-sea interface are frequently used to determine the CO2 flux between the ocean and the atmosphere. Little attention has been paid to the influence of variability in wind speed on the calculated gas transfer velocities and the possibility of chemical enhancement of CO2 exchange at low wind speeds over the ocean. The effect of these parameters is illustrated using a quadratic dependence of gas exchange on wind speed which is fit through gas transfer velocities over the ocean determined by the natural-14C disequilibrium and the bomb-14C inventory methods. Some of the variability between different data sets can be accounted for by the suggested mechanisms, but much of the variation appears due to other causes. Possible causes for the large difference between two frequently used relationships between gas transfer and wind speed are discussed. To determine fluxes of gases other than CO2 across the air-water interface, the relevant expressions for gas transfer, and the temperature and salinity dependence of the Schmidt number and solubility of several gases of environmental interest are included in an appendix.