Climate Science 101

Climate Basics

Since the industrial revolution, human emissions of greenhouse gases (GHG) have drastically altered the earth system[1, Topic 1]. Greenhouse gases have an insulating effect; they allow solar radiation to pass through the atmosphere but reflect outgoing radiation back to the earth’s surface. Unequivocal evidence links these emissions and the resulting impacts of global heating to human activity[1, Topic 1.3]. Namely, chemical (isotopic) signatures in the GHGs currently warming the planet match those of fossil fuels. To date, human-induced emissions are estimated to have caused almost 1°C of heating above pre-industrial levels, with numerous impacts already being felt around the world[2, A.1].

Timescale and Irreversibility[1, Topic 2.4] 

GHG emissions have persistent effects. A CO2 molecule released today may stay in the atmosphere for thousands of years. Positive feedbacks occur when climate change impacts in turn accelerate the climate change that was the root cause (e.g. sea ice in the Arctic). Negative feedbacks, such as CO2 fertilization of plants, slow down climate change. Positive feedbacks are expected greatly to outweigh negative feedbacks in the coming years. Some geophysical systems are unstable and can be pushed irreversibly past tipping points, such as the collapse of the Greenland ice sheet. The continued rapid growth of GHG emissions coupled with the potential for irreversible change communicates a central point: this is an emergency that requires immediate action (see Climate Crisis 101).

Emission Scenarios and Carbon Budgets

Emissions scenarios are projections of future GHG concentrations that correspond to different mitigation pathways (E.g. 1.5°C, 2°C). In its declaration of a climate emergency, UBC has committed to doing what it can to align with a pathway to 1.5°C. Globally, this pathway means we need a 45% reduction in net global emissions by 2030 and to achieve net-zero emissions by 2050; all relative to a 2010 baseline[2, C.1]. 

A carbon budget comes naturally from these scenarios; it refers to the remaining amount of carbon that could be emitted in a given scenario. To have a 50-66% chance of stabilizing global heating below 1.5°C, the global carbon budget is estimated to fall between 570 and 770 GtCO2e[2, C.1.3]. An important distinction to note is that the responsibility to contribute to mitigation efforts across the globe is not, and should not, be evenly distributed. Countries that have emitted more historically or have a greater capacity to mitigate emissions (E.g. Canada) are expected to do more. This is the concept of ‘fair sharing’, which makes clear that Canada’s emission reductions need to be stricter than the global average. 

Impacts

The impacts of climate change tend to be differentiated between Natural and Human systems. A snapshot of the major impacts across each system, as identified in the IPCC 1.5 report[3], include: 

• Natural Systems: increased overall average temperatures, increased frequency of drought and heavy rainfall events, rises in sea level and acidification, reduced ocean O2 levels, biodiversity and ecosystem loss (e.g. >99% loss of coral reefs  at 2°C of warming), species range shifts, sea ice loss and mountain glacier loss.
• Human Systems: adverse health effects (heat related illnesses, ozone related mortality, vector-borne diseases), increased frequency of water stress and undernutrition, reduced food availability, increased levels of poverty an d outmigration, increased exposure to extreme weather events, increased economic risk, and increased exposure to multiple compounding impacts.

All of these impacts are more severe in a 2°C  pathway than a 1.5°C pathway[3]; the risks are not distributed evenly across lines of race, identity, income or country of residence. This makes climate change a social justice issue (see Climate Justice 101).  Northern regions are experiencing many of these changes at a far greater rate than the rest of the world[3]. And critically, these impacts, though explained globally, are felt locally. 

Using the Science

The scientific consensus represented by the IPCC reports articulates the critical state of the climate and the urgency with which we must respond. Climate science can be stark but it can also chart a pathway forward. Often it asks a simple question: “can we turn this around?” The answer is resoundingly yes. Past and present emissions will not push global heating past the global target of 1.5°C[2, A.2]. In other words, there is still room to reimagine the future. To start thinking about what that response means at UBC, read UBC’s Role 101.