World Scientists’ Warning of a Climate Emergency

Scientists have a moral obligation to clearly warn humanity of any catastrophic threat and to “tell it like it is.” On the basis of this obligation and the graphical indicators presented below, we declare, with more than 11,000 scientist signatories from around the world, clearly and unequivocally that planet Earth is facing a climate emergency

World scientists' warnings into action, local to global

‘We have kicked the can down the road once again – but we are running out of road.’ – Rachel Kyte, Dean of Fletcher School at Tufts University. We, in our capacities as scientists, economists, governance and policy specialists, are shifting from warnings to guidance for action before there is no more ‘road.’ The science is clear and irrefutable; humanity is in advanced ecological overshoot. Our over exploitation of resources exceeds ecosystems’capacity to provide them or to absorb our waste. Society has failed to meet clearly stated goals of the UN Framework Convention on Climate Change. Civilization faces an epochal crossroads, but with potentially much better, wiser outcomes if we act now. What are the concrete and transformative actions by which we can turn away from the abyss? In this paper we forcefully recommend priority actions and resource allocation to avert the worst of the climate and nature emergencies, two of the most pressing symptoms of overshoot, and lead society into a future of greater wellbeing and wisdom. Humanity has begun the social, economic, political and technological initiatives needed for this transformation. Now, massive upscaling and acceleration of these actions and collaborations are essential before irreversible tipping points are crossed in the coming decade. We still can overcome significant societal, political and economic barriers of our own making. Previously, we identified six core areas for urgent global action – energy, pollutants, nature, food systems, population stabilization and economic goals. Here we identify an indicative, systemic and time-limited framework for priority actions for policy, planning and management at multiple scales from household to global. We broadly follow the ‘Reduce-Remove-Repair’ approach to rapid action. To guide decision makers, planners, managers, and budgeters, we cite some of the many experiments, mechanisms and resources in order to facilitate rapid global adoption of effective solutions. Our biggest challenges are not technical, but social, economic, political and behavioral. To have hope of success, we must accelerate collaborative actions across scales, in different cultures and governance systems, while maintaining adequate social, economic and political stability. Effective and timely actions are still achievable on many, though not all fronts. Such change will mean the difference for billions of children and adults, hundreds of thousands of species, health of many ecosystems, and will determine our common future

Integrating solutions to adapt cities for climate change

Record climate extremes are reducing urban liveability, compounding inequality, and threatening infrastructure. Adaptation measures that integrate technological, nature-based, and social solutions can provide multiple co-benefits to address complex socioecological issues in cities while increasing resilience to potential impacts. However, there remain many challenges to developing and implementing integrated solutions. In this Viewpoint, we consider the value of integrating across the three solution sets, the challenges and potential enablers for integrating solution sets, and present examples of challenges and adopted solutions in three cities with different urban contexts and climates (Freiburg, Germany; Durban, South Africa; and Singapore). We conclude with a discussion of research directions and provide a road map to identify the actions that enable successful implementation of integrated climate solutions. We highlight the need for more systematic research that targets enabling environments for integration; achieving integrated solutions in different contexts to avoid maladaptation; simultaneously improving liveability, sustainability, and equality; and replicating via transfer and scale-up of local solutions. Cities in systematically disadvantaged countries (sometimes referred to as the Global South) are central to future urban development and must be prioritised. Helping decision makers and communities understand the potential opportunities associated with integrated solutions for climate change will encourage urgent and deliberate strides towards adapting cities to the dynamic climate reality.Peer reviewe

THE ROLE OF d-π\pi ORBITALS IN SPIN-ORBIT COUPLING

$^{1}$D. S. McClure, J. Chem. Phys. 20, 682 (1952).""Author Institution: Department of Chemistry, Williams CollegeSpin-orbit coupling in p-$\pi$ aromatic molecules is known to be extremely small. Transitions between the lowest $\pi, \pi^{*}$ triplet state and the ground state (T $S_{\eta}$) are found to be very weak and largely polarized out of plane despite selection rules that would allow in-plane polarized intensity. Within the framework of LCAO-MO approximations it has been shown by $McClure^{1}$ that the smallness of the spin-orbit interaction arises from the vanishing (by symmetry) of one- and two-center spin-orbit coupling integrals that mix singlet $\pi, \pi^{*}$ and triplet $\pi, \pi^{*}$ states. This leaves only small three and four center terms to provide in-plane polarized intensity. It is found, however, that some of these one- and two-center integrals do not vanish for molecules containing atoms with d-$\pi$ orbitals. These terms are calculated for thiophene ($C_{4} H_{4}S$), and are found to make a significant contribution to spin-orbit coupling beyond that usually associated with heavy atom substitution. This contribution should introduce appreciable in-plane polarized intensity into the T $S_{\eta}$ transition of thiophene. The implications of these ideas for the increased spin-orbit coupling in halogen (and other heavy atom) substituted aromatic molecules, and in paired spin poryphyrins is also considered

SOLVENT EFFECTS ON SEVERAL TRANSITIONS OF TETRAZINE

Author Institution:We have previously discussed the electronic absorption and fluorescence, spectra of hydrogen bonded tetrazine which suggests the existence of both singly and doubly hydrogen bonded species in the ground and lowest excited $n\pi^{*}$ singlet state. We will present newly obtained fluorescence spectra in the region 540-650 nm which strongly support this earlier contention. In the region between 190 and 240 nm we have observed two weak, vibronic bands which shift together toward higher energy upon the addition of alchohol. This observation strongly suggests that these bands belong to a second previously unreported $n\pi^{*}$ transition. The effect of hydrogen bonding on the broad $n\pi \pi^{*}$ transition at 280 nm and on other spectral features in this region will also be discussed

HYDROGEN BOND STRENGTH DIFFERENCES IN THE nπ∗n\pi^{*} STATES OF THE DIAZINES AND TETRAZINE

Author Institution:Generally speaking, hydrogen bonds to the lone pairs of nitrogen heterocycles are expected to dissociate in $n\pi^{*}$ excited states. We have recently shown that this is not necessarily the case for pyrazine and tetrazine when bonded to very acidic alcohols. In the present study we present spectroscopic evidence that the expected hydrogen bond breaking does occur in the diazines pyridazine and pyrimidine. These results are surprising in that both of these molecules in the ground state are more basic and form stronger hydrogen bonds than either pyrazine or tetrazine. These differences suggest that there may be two different ""types"" of $n\pi^{*}$* electronic states in azines containing more than one nitrogen. A suggested explanation for these differences, based upon theoretical calculations for pyrazine, will be presented