FAQ

No. These authors showed that the influence of solar variation on global temperature from 1980 to 2010 (0.12 degrees) was far smaller than global warming for the same time interval (0.6 degrees) and in the wrong direction, meaning that solar variation alone would have caused cooling, not warming. That the impact of human-induced global warming far exceeds that of not only solar variation but also volcanic activity is further confirmed by the IPCC in their 6th assessment report. Finally, observations reported by these authors show that warming of the atmosphere is largely restricted to the lower part of the atmosphere - a fingerprint of human-induced warming. Solar variations would be expected to affect not only the lower, but also the upper atmosphere.

Yes, but only if we carry on. A mass extinction is characterized by the Earth losing more than 75% of its species in a (geologically) short period of time. Mass extinctions have happened five times since the explosion of life 541 million years ago. These authors have shown that, at present, species are going extinct faster than is geologically normal. This is a warning sign of a possible mass extinction. One of the reasons that this is happening is that by burning fossil fuels, we are heating the Earth faster than, and (if we carry on) we will heat the Earth more than the thresholds of temperature change for mass extinctions. This causes the habitats in which species live to move very quickly. These authors show that a rising number of species can’t keep pace with their moving habitats, putting them at risk of extinction.

No, but they can help a bit. Biofuels are fuels which come mostly from plants. They can provide an alternative to fossil fuels, especially for the transport sector. These authors write that the global warming potential of some (but not all) biofuels is lower than fossil fuels. The IPCC include biofuels among options available now to reduce greenhouse emissions but note that, for transportation, other options (e.g., a shift to public transportation) are considerably cheaper. The aforementioned authors further note that relying on biofuels to reduce emissions comes with other impacts, e.g., acidification, eutrophication, water shortages and biodiversity loss.

No. There are 3 categories of solutions to the climate and biodiversity crisis. These are emissions reduction, nature-based solutions (e.g., planting trees, protecting natural forests, restoring wetlands) and carbon dioxide removal (e.g., CCS). The IPCC have compared a number of different solution pathways.  All of them show that we need to implement all 3 solutions at the same time to achieve net-zero emissions. When we offset our emissions, we replace emissions reductions (one of the solutions) with nature-based solutions (another one of the solutions). This makes no sense because we needed both solutions to solve the climate and biodiversity crisis.

Since 1896. Svante Arrhenius made the connection that by burning fossil fuels we would make the Earth warmer, and wrote about it in a paper which was published in 1896.

Fossil fuels (coal, oil and gas) contain carbon which was captured from the air by living things (plants, plankton, algae) over millions of years. When we burn fossil fuels, we put lots of that carbon back in the air all at once. These authors have shown that no natural process exists that can remove all of that carbon anything like as fast as we are adding it and that a lot of it stays in the air as CO2 (a greenhouse gas). This makes the Earth hotter, causing the climate and biodiversity crisis.

Yes. Aerosols (very small particles) emitted by humans (e.g., when we burn stuff) tend to cool the climate by reflecting some sunlight back into space. However, this effect is short-lived because aerosols only remain in the atmosphere for a short time (a week or so). This can temporarily mask the warming effect of CO2 emitted by humans, which (unlike aerosols) carries on affecting the climate for many hundreds of years. This masking effect is regional because aerosols fall out of the sky fairly quickly. These authors link faster warming in Europe partly to a reduction of this masking effect that was brought about by efforts to reduce aerosols emissions in the region. In contrast, continued emissions of aerosols carry on masking greenhouse warming in many developing countries. Globally, this masking effect may be hiding an additional 0.5°C of greenhouse warming. However, as these authors have shown, the masking effect of aerosols on greenhouse warming is diminishing. This will, in turn, reveal the true scale of human-induced global warming.