Understand what are climate change and greenhouse gases
Open the page directory

2. Understand what are climate change and greenhouse gases, and analyse their causes and impacts

Chapter 1 - Why Can’t We Ignore Climate Change?

What’s The Big Deal If Our Climate Is Changing?

Many scientists have warned that climate change would lead to irreversible consequences to the world. Recently, students around the world were out on strikes to protest and demand actions on climate change. Nevertheless, some skeptics choose to disregard the projected impacts of climate change as scaremongering; some consider receding glaciers and habitat loss for polar bears of little relevance. They have been indifferent to climate change impacts, not to mention changing lifestyles to cope with it. In fact, the impacts of climate change are hitting increasingly close to home. From erratic weather patterns to the rising frequency of extreme events, all of us should be able to experience that climate change is already affecting every part of our lives, no one is spared.

Our lifestyles and consumption habits cause the rising temperatures globally. Therefore, all human beings need to bear the responsibilities for mitigating the impacts of climate change. According to the recent Special Report on Global Warming of 1.5°C of the Intergovernmental Panel on Climate Change (IPCC), it is evident that human-induced warming has already reached about 1°C above pre-industrial levels, and the warming rate is now about 0.2°C per decade. 1 Temperatures greater than the global average has also already been experienced in many regions and seasons. Also, according to the Global Risks Report 2018 published by the World Economic Forum, extreme weather events such as storm surges, droughts and natural disasters have been identified as the top risks that pose a serious threat to global stability. 2

Globally, annual emissions of carbon dioxide (CO2) have risen dramatically over the past decades. With more CO2 accumulated in the atmosphere, the atmosphere traps more thermal energy on the Earth. The more carbon we pump into the atmosphere, the higher the average temperature of the planet will be, and we expect to see more frequent extreme weather events causing sustained and serious impacts on health, the economy and the environment.

Gobal Temperature change
Source: NASA3

Carbon Emissions

Carbon emissions are sometimes used as a shorthand for referring to the emissions of CO2, or greenhouse gases (GHGs) in general. Strictly speaking, gases that absorb and trap heat on the planet are called GHGs. The main GHGs in the Earth’s atmosphere are CO2, methane (CH4), nitrous oxide (N2O) and ozone (O3).

CO2 is the most common GHGs emitted by human activities, in terms of the quantity released and the overall impact on global warming. They are mainly produced from the activities that involve the burning of fossil fuels (e.g. coal and natural gas), including electricity generation, travelling by car, ship and plane, etc. To facilitate the measurement and comparison, the emissions of different GHGs are converted to CO2-equivalent (CO2e)* based on GHG’s global warming potential.

Note: *CO2-equivalent (CO2e): A metric measure used to compare the emissions from various GHGs based upon their global warming potential (GWP). The CO2e for a gas is derived by multiplying the tonnes of the gas by the associated GWP.

We Simply Don’t Have Time

Scientists have warned that we have some 10 years left to limit climate change catastrophe. According to the special report published by the IPCC in October 2018, the projected climate change impacts are substantially worse at 2°C compared with 1.5°C. Meanwhile, it is necessary to acknowledge that achieving the 2°C target of the Paris Agreement is indeed challenging. The key issue will be on the discussion of how to meet the target through the more aggressive proposals and its feasibility. 4

Like other coastal cities, Hong Kong faces multiple climate-related threats, including rising temperatures and more extreme weather phenonmena such as violent storms and flooding rains. Unless the world takes bolder and swift actions to reduce GHG emissions, these intensifying impacts are expected to take place at an even more rapid pace in the coming decades. Hong Kong, as a responsible member of the global community, is taking proactive steps to combat climate change.

Projections for 2100

Extreme Heat

Global population exposed to severe heat at least once every 5 years

Global Average Temperature Rise
Sea Level Rise

Contribution to sea level rise by 2100

Global Average Temperature Rise
Plant Species Loss

Plants that lose at least half of their range

Global Average Temperature Rise
Crop Yields

Reduction in maize harvests in tropical areas

Global Average Temperature Rise

Decline in marine fisheries

Global Average Temperature Rise
Coral Reefs

Further decline in coral reefs

Global Average Temperature Rise

Learning materials

tips Challenges
Question 5