Planetary emittance and feedback parameters through varying climates in basic modelling

In search for reproducibility of the results from sophisticated scientific research, the present work focuses on the planetary (longwave) emittance variabilities. A simple model appears applicable through the entire range from very cold to extremely warm climates and for different climate driving forces, i.e. solar luminosity variation and CO2 concentration change. The results interrelate effects from lapse rate, water vapor, CO2, and clouds for equilibrium climate states. Feedback parameters are analysed for the emittance decomposition into the atmospheric window, clouds, and the cloud-free atmosphere. A view is devoted to the faint young Sun problem.

Chance played a role in determining whether Earth stayed habitable

Earth’s climate has remained continuously habitable throughout 3 or 4 billion years. This presents a puzzle (the ‘habitability problem’) because loss of habitability appears to have been more likely. Solar luminosity has increased by 30% over this time, which would, if not counteracted, have caused sterility. Furthermore, Earth’s climate is precariously balanced, potentially able to deteriorate to deep-frozen conditions within as little as 1 million years. Here I present results from a novel simulation in which thousands of planets were assigned randomly generated climate feedbacks. Each planetary set-up was tested to see if it remained habitable over a period of 3 billion years. The conventional view attributes Earth’s extended habitability solely to stabilising mechanisms. The simulation results shown here reveal instead that chance also plays a role in habitability outcomes. Earth’s long-lasting habitability was therefore most likely a contingent rather than an inevitable outcome.

Modeling Quiet Solar Luminosity Variability from TSI Satellite Measurements and Proxy Models during 1980–2018

A continuous record of direct total solar irradiance (TSI) observations began with a series of satellite experiments in 1978. This record requires comparisons of overlapping satellite observations with adequate relative precisions to provide useful long term TSI trend information. Herein we briefly review the active cavity radiometer irradiance monitor physikalisch-meteorologisches observatorium davos (ACRIM-PMOD) TSI composite controversy regarding how the total solar irradiance (TSI) has evolved since 1978 and about whether TSI significantly increased or slightly decreased from 1980 to 2000. The main question is whether TSI increased or decreased during the so-called ACRIM-gap period from 1989 to 1992. There is significant discrepancy between TSI proxy models and observations before and after the gap, which requires a careful revisit of the data analysis and modeling performed during the ACRIM-gap period. In this study, we use three recently proposed TSI proxy models that do not present any TSI increase during the ACRIM-gap, and show that they agree with the TSI data only from 1996 to 2016. However, these same models significantly diverge from the observations from 1981 and 1996. Thus, the scaling errors must be different between the two periods, which suggests errors in these models. By adjusting the TSI proxy models to agree with the data patterns before and after the ACRIM-gap, we found that these models miss a slowly varying TSI component. The adjusted models suggest that the quiet solar luminosity increased from the 1986 to the 1996 TSI minimum by about 0.45 W/m2 reaching a peak near 2000 and decreased by about 0.15 W/m2 from the 1996 to the 2008 TSI cycle minimum. This pattern is found to be compatible with the ACRIM TSI composite and confirms the ACRIM TSI increasing trend from 1980 to 2000, followed by a long-term decreasing trend since.

Mass-loss varying luminosity and its implication to the solar evolution

Several models of the solar luminosity, , in the evolutionary timescale, have been computed as a function of time. However, the solar mass-loss, , is one of the drivers of variation in this timescale. The purpose of this study is to model mass-loss varying solar luminosity, , and to predict the luminosity variation before it leaves the main sequence. We numerically computed the up to 4.9 Gyrs from now. We used the solution to compute the modeled . We then validated our model with the current solar standard model (SSM). The shows consistency up to 8 Gyrs. At about 8.85 Gyrs, the Sun loses 28% of its mass and its luminosity increased to 2.2. The model suggests that the total main sequence lifetime is nearly 9 Gyrs. The model explains well the stage at which the Sun exhausts its central supply of hydrogen and when it will be ready to leave the main sequence. It may also explain the fate of the Sun by making some improvements in comparison to previous models.