Global challenges GHGs and ocean acidification cuz I’m stupid

What is radiative forcing?

Incoming energy - outgoing energy

Relative to the year 1750

What are feedback responses for increased surface temperature?

Higher clouds, increased water vapour, increased albedo and biogeochemical feedback, increased vegetation growth

What does the UNFCC stand for?

The United Nations Framework Convention on Climate Change (seems for the stabilization of greenhouse gas)

What is the albedo effect?

Dark surfaces (low albedo) absorb radiation and get heated, light surfaces (high albedo) reflect radiation and have a cooling effect

Aerosols with high albedo can scatter light and reflect it back into space with a cooling effect

What happens if there are more cloud condensation nuclei?

Heightened albedo and radiation reflection occurs

Cloud lifetime is increased

Droplet size reduces

What are the most abundant greenhouses gases?

Water vapour

Carbon dioxide (420ppm)

Methane

Nitrous oxide

CFCs

Which GHGs are the most to least warming?

CFC

CF4

Ozone

Nitrous oxide

Methane

Co2

What greenhouse gases are in the atmosphere for the longest to shortest time?

CF4 - 50,000 yrs

Nitrous oxides - 121 yrs

CFC - 45 yrs

HFC - 13.4

CH4 - 12.4

Why is it good to get rid of “short lived climate forcing” GHGs?

It cools the atmosphere faster

How much did the global methane pledge aim to cut methane by 2030?

30%

Which gas contributes the most to greenhouse effect between CO2, water vapour and methane?

Water vapour (36 to 70%) then CO2 (9 - 26%), then methane (4-9%)

What polluting gases have the highest cooling effect?

SO2 (sulphur dioxide), nitrate, organic aerosols

How many premature deaths are caused by pollution?

7 million (due to asthma, heart disease, stroke, lung cancer etc)

Which short-lived climate forced has the largest warming effect?

Methane, followed by ozone

What degree of warming should we aim to limit to at all costs and why?

Max 2C but preferably less than 1.5C as severe environmental impacts prevented by this limit

Examples of NETs (negative emission technology)

Planting trees, biochar, soil carbon sequestration

What are the two largest sources of organic atmospheric methane?

Wetlands, followed by livestock

How much methane does wetlands, fossil fuel extraction, and livestock produce?

Wetlands - 161.6 million tonnes per year

Fossil fuel extraction - 129.5 million tonnes per year

Livestock - 103 million tonnes per year

What is the equation for aerobic methanotrophs (methane oxidisers)

CH4 + O2 → biomass + ATP

What is the enzyme used in aerobic methanotrophs?

methane monooxygenase

How much methane is released to the atmosphere every year?

Around 800 million tonnes

How much GHGs released from dams is methane?

79%

Why do reservoirs/dams release CH4?

Floods vegetation, which goes anoxic and releases CH4 as it decomposes

Pressure change from gases exiting the dam causes gas release

High CO2 impact on global temperatures and surface temperatures

~ 0.2C decade over 30 years

~ 0.6 - 0.76C over last 100 years

Up to 7C over next 100 years

Do native or invasive barnacles respond better to CO2 and temp increase?

Natives respond better with more growth, invasive have lower growth rates

Is sensitivity to low oxygen higher in early life fish?

Yes - this also reduces fitness if this species and can impact the food chain

In comparison to current sea levels, how high/low was sea levels in the last interglacial and last ice age?

Interglacial - 5m higher

Ice age - >100m lower

What is the mean sea level?

The average height of the sea over longer periods of time (month or year)

Evidence for increases in rate of MSL

During 19th and early 20th centuries sea level rise was ~ 1.7mm year

Late 20th to 21st century ~ 3.3mm year

What are the characteristics of the most vulnerable regions to sea level rise?

Coastal areas with dense populations, low elevations, appreciate rates of subsidence, land subsidence, inadequate adaptive capacity

What are the main three contributors to MSLR

Glaciers

Ice sheets

Thermal expansion

What seasonal issues have rising temperatures caused to glaciers and ice caps

Greater than average summer melting

Reduced snowfall in winter and generally

Impacts of MSLR on water

Greater wave height, greater wave driven run-up, raised ground water levels, salinised freshwater lens

What are the erosion rates of white cliffs?

22-33cm year -1

Clay cliffs (like Yorkshire) 2m a year

Why does MSLR lead to inundation?

Because the water table rises

What is the estimated amount of carbon in soils?

~1500 to 2400 PgC, with Permafrost containing an additional ~1700 PgC

How much carbon do atmosphere, vegetation and oil reserves contain?

Atmosphere: 730PgC

Vegetation: 450-650PgC

Oil reserves: 173-264PgC

What are the 7 soil functions described by the European Commission?

1) Biomass production (agriculture and forestry

2) Storing, filtering, transforming nutrients

3) Biodiversity pool

4) Carbon Pool

5) Cultural and recreational activity

6) Source of raw material

7) Archive of geological and archaeological heritage

What is soil?

Humus and mineral components

What is humus?

Carbon that has resisted degradation - very slowly decomposed and dark in colour with active microbial community

Which soil horizon is the most biologically active?

The A horizon is the most biologically active layer with more organic matter and nutrients

Why is cation exchange in soils important?

It’s critical for nutrient retention

Explain cation exchange capacity (CEC)

Colloids- smallest particles of clay and humus are mostly negatively charged

Negatively charged particles bind to cations, which are important nutrients for plants such as magnesium, potassium and calcium

Plant roots release protons (H+ ions) which results in cation exchange between this and the minerals

Too much acid in soils can leach out these nutrients and lead to poor CEC

What is soil fertility?

The ability to sustain plants

What affects soil fertility?

PH, salinity, microbes, bioavailable phosphate, nutrient abundance and balance, type of clay (particle size), toxic elements

What GHG uptake processes occur in and on forest soils?

CO2 uptake via photosynthesis and primary production

CH4 uptake via methane-oxidising soil bacteria

What are the GHG efflux/release processes that occur in and on forest soils?

CO2 efflux through autotrophic and heterotrophic respiration

N2O (nitrous oxide) efflux through microbial nitrification and denitrification processes

Why do bigger trees fix more carbon?

Larger leaf area per tree

Does stand productivity increase or decrease with tree age?

Decrease, as tree density decreases with age

What proportion of global carbon do peatland “soils” hold?

1/3

(in the UK an estimated 3 billion tonnes of carbon stored)

What % of earth do peatlands cover?

3%

What does a high water table cause in peatlands?

Anoxia, slow decomposition and release of CH4 emissions

What % of global atmospheric CH4 do peatlands release?

10%

Why does Sphagnum moss decompose slowly?

Soil is flooded so it’s anoxic/anaerobic, nutrient poor and acidic

How much agricultural land is moderately or severely affected by land degradation?

52%

How much land is lost to drought and desertification each year?

12 million hectares

How much of the world’s poor people are directly affected by land degradation?

74%

What are bare soils vulnerable to and affected by?

Soil compaction by livestock and machinery, wind erosion, water erosion

How much does 1mm soil from 1 hectare of water erosion weigh?

4.5 tons

What is chemical degradation?

Depletion of organic matter and nutrients

Contamination with chemical pollutants

Salinization in dry areas (salinization is poor water management and too much water evaporates from the surface, salts are left behind and is toxic to plants)

Desertification - occurring in arid, semi-arid areas and sub-humid areas

Why is acid rain detrimental to plants?

It makes the soil acidic and stops CEC (cation exchange) on soil colloids with proteins

1) it displaced nutrients from cation exchange sites, leaches away and is not available for plant growth

2) toxic aluminium is soluble in at low pH which injures plants and soil microorganisms

Acidity can also result from excessive ammonium fertilisation via nitrification by soil microbes (NH4+ → NO3- + H+)

What the four major causes of soil degradation?

Water erosion (56%), wind erosion (28%), chemical degradation (12%) and physical degradation (4%)

What are the main underlying causes of soil degradation?

Overgrazing (35%), Deforestation (30%), Agricultural activity (27%), overuse of vegetation e.g. for fuel (7%) and industrial activity (1%)

What happens to yield plateaus as soil degradation gets worse? What’s the wheat example?

It likely gets worse due to climate change, e.g. wheat has a 6% yield decrease per 1C rise in temp