Research

Reconstruction of Earth’s past energy imbalance

(Preprint, Poster AGU24, GitHub)

a Global-mean surface temperature reconstruction over 850–2000, expressed as anomalies relative to 1961–1990. Our reconstruction, based on climate proxies like tree rings and corals, agrees well with instrumental products over the historical period. The thick black line is the ensemble mean, the thinner lines are individual ensemble members, all of which are consistent with the proxies. b Our reconstruction of Earth's energy imbalance over the pre-industrial period provides context for the current energy gain measured by satellites. The 21st-century trend in energy gain exceeds any value that can be explained by natural variability, indicating a human influence.

My current research focuses on reconstructing Earth’s energy imbalance over the last millennium (850–2000). The energy imbalance is the most fundamental metric of climate change, yet our observational record is short and coupled climate models have large uncertainties. We extend the observational energy budget record by 1000 years based on climate proxies such as tree rings, corals, and ice cores. Our reconstruction shows that a cooling trend over the last millennium was accompanied by persistent energy loss and sea ice growth. We reaffirm the role of volcanic clusters in driving this cooling trend through the accumulation of heat loss. By extending the existing record into the pre-industrial period, we also provide context for natural energy budget variability in the absence of anthropogenic forcing such as greenhouse gases. Our reconstruction reveals that the current energy gain and its increasing trend, which are the fundamental drivers of global climate change, are unprecedented relative to the period before strong human influence on the climate. This work is advised by Greg Hakim.

High-accuracy radiation pressure models

(Paper, GitHub)

Ground track of LRO for one orbit, colored by the irradiance due to lunar albedo. This irradiance is calculated from the incident solar radiation and a spherical harmonics expansion of the albedo distribution. A spacecraft model then takes the direct solar and lunar albedo radiation to estimate the acceleration due to radiation pressure, resulting in small orbital perturbations.

For this work, we investigated the effect of radiation pressure on the Lunar Reconnaissance Orbiter (LRO). We compared models of varying complexity to determine the benefits and computational cost of high-accuracy radiation pressure modeling. These models are necessary for precision orbit determination, which is a prerequisite for LRO’s geodetic mission objectives. We implemented models for both the spacecraft and radiation sources in the Tudat numerical astrodynamics framework. We found that accurate spacecraft models are necessary to account properly for changing orientation and geometry, but complex lunar models have little benefit over simpler ones. This work was advised by Dominic Dirkx.