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With research staff from more than 70 countries, and offices across the globe, IFPRI provides research-based policy solutions to sustainably reduce poverty and end hunger and malnutrition in developing countries.

researcher spotlight

Timothy Thomas

Timothy Thomas is a Senior Research Fellow in the Foresight and Policy Modeling Unit. His research focuses on the impact of climate change on agricultural productivity. Tim’s work involves developing innovative methods for simulated climate futures and model coordination between climate, crop, water, energy, and economics.

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Foresight and Policy Modeling

Tamunotonye Braide

Senior Research Officer

Bio

Tamunotonye Braide is a Senior Research Officer with the Foresight and Policy Modeling Unit, and is working in an outposted capacity.

Foresight and Policy Modeling

Publications

Resource thumbnail

Working Paper

Predicting agricultural productivity under climate change using crop yield emulator

2026Braide, Tamunotonye M.; Thomas, Timothy S.; Robertson, Richard D.
Details

Predicting agricultural productivity under climate change using crop yield emulator

This study develops a crop yield emulator as a computationally efficient alternative to the DSSAT process-based model, enabling fast, large-scale assessments of how temperature, rainfall, CO2, and nitrogen influence crop yields. Implemented using fixed-effects polynomial regression in R, the emulator was trained on DSSAT outputs and validated across seven globally important crops, maize, wheat (spring and winter), rice (indica and japonica), soybeans, sorghum, groundnuts, and potatoes. It showed high predictive accuracy (R2 > 0.90) for most crops, especially spring wheat, groundnut, and potato, and performed reliably under climate scenarios such as RCP7.0. The emulator captured key crop-specific responses, such as maize’s sensitivity to heat and nonlinear yield responses to nitrogen inputs. While its performance is slightly lower for maize and Indica rice compared to other crops, it remains a scalable and cost-effective tool for climate scenario analysis. This tool offers valuable support for agricultural decision-making and climate adaptation planning by enabling rapid, data-driven insights into yield outcomes under future conditions.

Year published

2026

Authors

Braide, Tamunotonye M.; Thomas, Timothy S.; Robertson, Richard D.

Citation

Braide, Tamunotonye M.; Thomas, Timothy S.; and Robertson, Richard D. 2026. Predicting agricultural productivity under climate change using crop yield emulator. IFPRI Modeling Systems Technical Paper 5. Washington, DC: International Food Policy Research Institute. https://hdl.handle.net/10568/183869

Keywords

Agricultural Productivity; Climate Change; Crop Yield; Yield Forecasting; Nitrogen; Carbon Dioxide; Regression Analysis

Language

English

Access/Licence

Open AccessCC-BY-4.0

Source

Source record

Project

Foresight

Record type

Working Paper

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Working Paper

Creating a taro yield emulator and using it to study climate change impact on taro in Papua New Guinea

2026Braide, Tamunotonye M.; Thomas, Timothy S.; Robertson, Richard D.
Details

Creating a taro yield emulator and using it to study climate change impact on taro in Papua New Guinea

This paper develops a taro yield emulator to assess climate change impacts on taro production in Papua New Guinea (PNG). The emulator uses a fixed-effects polynomial regression trained on DSSAT simulations to capture non-linear, stage-specific responses of taro yields to rainfall and temperature. Historical MSWX weather and future climates from CMIP6/ISIMIP3b and a large MIT-IGSM/AgERA5 sample are used to drive the emulator and assess changes in average yields, yield variability, and the frequency of low-yield years across PNG. Our analysis shows that taro appears to be sensitive to both low- and high-rainfall levels during particular phases of growth and is sensitive to heat during particular phases, as well. Our visit to farmers fields in the Markham Valley along with discussions with experts at GrowPNG in Lae, NARI, and PNG University of Technology in Lae alerted us to the fact that drought was a serious problem for taro, but the model revealed the additional issues with high rainfall and high temperature, along with the additional information about the months that were particularly important for determining the degree of damage that adverse weather might do to yields. National-average yield changes by mid-century under high-emissions scenarios are projected to be small based on the median projections across climate models, however one of the climate models projects a much larger temperature increase relative to the other models, and for that climate model, the yield reduction is around 9% on average.

Year published

2026

Authors

Braide, Tamunotonye M.; Thomas, Timothy S.; Robertson, Richard D.

Citation

Braide, Tamunotonye M.; Thomas, Timothy S.; and Robertson, Richard D. 2026. Creating a taro yield emulator and using it to study climate change impact on taro in Papua New Guinea. Papua New Guinea Working Paper. Washington, DC: International Food Policy Research Institute. https://hdl.handle.net/10568/182470

Country/Region

Papua New Guinea

Keywords

Oceania; Taro; Crop Yield; Climate Change; Impact; Climate Change Impacts; Crop Modelling; Fixed Costs; Regression Analysis

Language

English

Access/Licence

Open Access

Source

Source record

Record type

Working Paper

Resource thumbnail

Brief

Climate change and the impact on taro in Papua New Guinea

2025Braide, Tamunotonye; Thomas, Timothy S.; Robertson, Richard D.
Details

Climate change and the impact on taro in Papua New Guinea

In this paper we present a brief summary of recent historical climate of Papua New Guinea (PNG), finding that rainfall has been increasing greatly compared to pre-1995 levels, but that temperature has only been rising at a moderate rate. We then examine the 5 climate models used in this study from the Inter-governmental Panel on Climate Change (IPCC) / ISIMIP / CMIP3b, discovering one – IPSL – which best reflects the climate trends noted in PNG since 1995. The climate model projections show that temperature changes in PNG are expected to be less than most other places in the world and precipitation changes in PNG are projected to be higher than most other places in the world. Despite noting that IPSL seems to best represent climate changes observed thus far, we use all 5 climate models in the DSSAT crop model for taro, investigating how each climate model will lead to changes in taro yields at each half-degree pixel. In the aggregate, we find that the IPSL model leads to the greatest projected reduction in taro yield at -6.4% for the nation, with Southern region projected to have greater than 10% yield reduction for taro. Across the 5 climate models, the median across model results suggest only a 1.6% yield reduction, while the most optimistic model projects a 4.4% gain. Because of uncertainty across climate models and different impacts across regions, as well as potentially increasing climate variability which would lead to more extreme events including droughts and floods, we recommend developing a suite of options to help farmers navigate future climate uncertainty. For example, developing and testing crop varieties that would offer better yields whether the future is wetter or drier, as well as varieties that are less sensitive to temperature extremes. These could include new varieties of taro but might also include alternative crops and farming techniques designed to protect the plants during ad-verse climate events.

Year published

2025

Authors

Braide, Tamunotonye; Thomas, Timothy S.; Robertson, Richard D.

Citation

Braide, Tamunotonye; Thomas, Timothy S.; and Robertson, Richard D. 2025. Climate change and the impact on taro in Papua New Guinea. Papua New Guinea Project Note 19. Washington, DC: International Food Policy Research Institute. https://hdl.handle.net/10568/173654

Country/Region

Papua New Guinea

Keywords

Oceania; Climate Change; Crop Yield; Rainfall; Taro

Language

English

Access/Licence

Open AccessCC-BY-4.0

Source

Source record

Project

Climate Resilience

Record type

Brief