For these simulations, we do not use a time-dependent model of the
albedo and XCE, rather we take
two representative values: high (albedo = 0.7, XCE = 0.55) indicative of late times, and low (albedo =
0.5; XCE = 0.4) indicative of early times.
Later, we
add a third, intermediate, combination (albedo = 0.5, XCE = 0.55).