Photophysical oxidation of HCHO produces HO radicals.

Formaldehyde, HCHO, is the highest-volume carbonyl in the atmosphere. It absorbs sunlight at wavelengths shorter than 330 nm and photolyses to form H and HCO radicals, which then react with O to form HO. Here we show HCHO has an additional HO formation pathway.

Response to Comment on "A global environmental crisis 42,000 years ago".

Our paper about the impacts of the Laschamps Geomagnetic Excursion 42,000 years ago has provoked considerable scientific and public interest, particularly in the so-called Adams Event associated with the initial transition of the magnetic poles. Although we welcome the opportunity to discuss our new ideas, Hawks’ assertions of misrepresentation are especially disappointing given his limited examination of the material.

Response to Comment on "A global environmental crisis 42,000 years ago".

Our study on the exact timing and the potential climatic, environmental, and evolutionary consequences of the Laschamps Geomagnetic Excursion has generated the hypothesis that geomagnetism represents an unrecognized driver in environmental and evolutionary change. It is important for this hypothesis to be tested with new data, and encouragingly, none of the studies presented by Picin . undermine our model.

A global environmental crisis 42,000 years ago.

Geological archives record multiple reversals of Earth's magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the Laschamps Excursion [41 to 42 thousand years ago (ka)]. We use ancient New Zealand kauri trees () to develop a detailed record of atmospheric radiocarbon levels across the Laschamps Excursion.

Systematic Characterization of Gas Phase Binary Pre-Nucleation Complexes Containing HSO + X, [ X = NH, (CH)NH, (CH)NH, (CH)N, HO, (CH)OH, (CH)O, HF, CHF, PH, (CH)PH, (CH)PH, (CH)P, HS, (CH)SH, (CH)S, HCl, (CH)Cl)]. A Computational Study.

A systematic characterization of gas phase binary prenucleation complexes between HSO (SA) and other molecules present in the atmosphere (NH, (CH)NH, (CH)NH, (CH)N, HO, (CH)OH, (CH)O, HF, CH F, PH, (CH)PH, (CH)PH, (CH)P, HS, (CH)SH, (CH)S, HCl, (CH)Cl) has been carried out using the ωB97X-D/6-311++(2d,2p) method at the DFT level of theory. A relationship between the energy gap of the SA's LUMO and the partner molecule's HOMO, and the increasing number of methyl groups -CH in the SA's partner molecule is provided. The binding energies of the bimolecular complexes are found to be related to the electron density in the hydrogen bond critical point, the HOMO-LUMO energy gap, the nature of the hydrogen acceptor atom, and the frequencies shift of acid OH bonds.