If humans are at the heart of the problem, we are also at the heart of its solution.  Notice how the air quality improved immediately—though sadly, only temporarily—when a lot of production came to a halt during the 2008 financial crisis, and again during the recent covid-19 pandemic.  Given the known effects of meat production on air quality and climate, we’re recommending a more plant-based diet, in line with the Chinese Dietary Guidelines 2016.  This is potentially game-changing, because it gives us ordinary folks the chance to do our bit, instead of assuming that it is up to governments and large corporations to solve the problem.

We’re also proposing that the current food production systems should adopt more sustainable practices to reduce their environmental impacts.  For instance, in one of our studies, we looked at the potential benefits of intercropping maize with soybeans.  The nitrogen-fixing properties of soybeans can provide additional nutrients, and this allows farmers to use much less synthetic, ammonia-releasing fertilizer, while getting the same amount of maize as they did before (plus some extra soybeans!).  This method can yield an increase of HK$460 billion in crop sales and save another HK$100 billion in public healthcare costs arising from air pollution.  Intercropping can also reduce greenhouse gas emissions from farmland.  Indeed, intercropping is a technique that has been practised by farmers for centuries.  It only died out in the 20th century, when agriculture became modernised, mechanised and monocultural.  There’s a lot we can learn from our ancestors!

Bear in mind, though, that efforts to protect the environment can have unintended consequences.  We tend to assume, for example, that planting trees is a good thing in all circumstances.  It is certainly true that afforestation can help cool down cities and enhance carbon uptake.  At the same time, our research also suggests that certain broadleaf trees release volatile organic compounds which react with car emissions to form ozone, a notorious air pollutant.  Needleleaf trees perform better in this respect, but they might reduce local biodiversity and even cause warming.  It’s not easy to balance the varying considerations involved, and researchers, city arborists and forest managers need to come together to make the best available choices.

According to the IPCC Report, it can no longer be denied that human influence has warmed the climate at an unprecedented rate.  Nothing like it has been seen in the thousands of years for which we have records.  Climate change is affecting every inhabited region across the globe, and human activities have undoubtedly contributed to many observed changes in weather and climate extremes.  Global warming is likely to go higher than 2°C above preindustrial level before the end of the 21st century.  If it does, it will lead to frequent heat extremes beyond the tolerance thresholds for agriculture and human health.  This catastrophic scenario can only be avoided if deep cuts in carbon dioxide and other greenhouse gas emissions occur in the coming few decades.

As an atmospheric scientist, I am excited about the advances in climate science documented in the Report.  More than ever, we are now able to understand better the complex working of the climate system and use computer models to make more accurate predictions of how climate change will progress in different regions.  The considerable progress made in policy-relevant scientific research is truly impressive.

But the Report also paints a bleak picture of our planet’s future.  Climate change is happening even more quickly than we feared.  Many human-induced changes due to past and future greenhouse gas emissions are in fact irreversible for centuries to millennia.  The current trajectory of socioeconomic development is likely to warm the Earth’s surface by mid-century to a level that can fuel natural disasters, weather extremes, food and water crises, mass migration and conflicts for the global population.  The burden will overwhelmingly be borne by countries in the developing world.

That said, I remain hopeful that if all nations work together to cut down carbon emissions and achieve net zero by 2050, we still have time to turn the tide and keep warming within 1.5°C.  Heaven knows, even this level is bad enough, but at least it’s tolerable.  The Report provides an array of reliable road maps that show policymakers how to achieve carbon neutrality at different time points over the next few decades.  Fortunately, the momentum for change seems to be growing.  In recent years we have seen a growing shift around the world towards renewable energy.  Thanks to the Report, we now know exactly what we need to do to avert catastrophe.  Now, we just need to get on with it.  The ball is now in our court.

I used to be quite a bug enthusiast when I was kid—not that I was very good at raising them, as a lot of my pet insects died earlier than they should have done.  Originally, I wanted to become a zoologist when I grew up, but then I realised I was more interested in the big picture—the interconnections among lives—than in focusing on just a few creatures.  The same thinking went into my decision to study environmental science and engineering instead of taking an offer to study medicine.  I wanted to try to fix the larger issues, and perhaps save more lives.

And so I went to MIT for a BSc and Harvard for a PhD in atmospheric science.  When I was a postdoctoral fellow at MIT, I heard about CUHK’s new programme in Earth System Science.  I’d always wanted to teach, as much as I wanted to develop a career in scientific research.  I am thankful for the opportunity to join CUHK as it puts equal emphasis on education and research, allowing us to pursue our passions to the fullest extent.