ENVR 2200 - Lecture 7

Water and Climate

What is latent heat?

Latent heat is the thermal energy absorbed or released by a substance during a change of physical state (such as melting, freezing, boiling, or condensing) without any change in its temperature.

What is sensible heat?

Sensible heat changes the temperature of a substance (making it hotter or colder) without changing its physical state

How many J are needed to evaporate 1 kg of water? What type of heat is this?

Evaporating 1 kg of water takes about 2.5 million J. This is latent heat

What is W/m2?

Watts per square meter and it measures how much energy passes through a specific area every second

What type of heat is the main way that the Earth’s surface loses energy?

Latent heat is the main way that the surface loses energy

What are three main roles that latent heat plays for the Earth?

Latent heat is the main way that the surface loses heat (temperature) and cools down, latent heat also moves heat poleward and upward, and latent heat powers storms

If you have a pot of water on a hot stove, the stove will heat the water up and the temperature will climb from 60 degrees to 100 to 212 degrees F or 100 C. You can feel thus heat and a thermometer can track it easily. What type of heat is this?

This is sensible heat. This is heat that you can feel

If you have a pot of water on the stove and it has heated up to 212 F or 100 C it is at its boiling point. The thermometer stops rising even though the stove is still blasting the water with heat. Where is all the extra heat going if the temperature of the water is not going up?

The extra heat is used to break the bonds holding the liquid water molecules together turning them into invisible gas (vapor). The heat from the stove is now trapped inside of the gas

What relation does the Clausius-Clapeyron suggest?

The Clausius-Clapeyron suggests that the amount of water vapor in the atmosphere increased by 7% per degree C warmer. The does not increase the amount of water vapor the atmosphere can hold, its just that the higher temperatures let more water vapor exist. It is not about capacity more so about temperatures allowing water vapor to exist

What is radiative forcing?

radiative forcing or forcing is an initial driver that changes Earth’s energy balance

What is an example of radiative forcing?

Human emissions of carbon dioxide is an initial driver that changes Earth’s energy balance which is radiative forcing

What is the difference between forcing and feedback?

Forcing is an initial driver that can change Earth’s energy balance while feedback is a secondary response after forcing occurs

Can water vapor start climate change?

No, water vapor cannot start climate change, it can only respond to initial climate change

What is the strongest positive feedback cycle in Earth’s climate system?

Water vapor is the strongest feedback cycle in Earth’s climate

How much excess heat has the ocean absorbed since 1970?

The ocean has absorbed 90% of the excess heat since 1970

How much does global precipitation rise based on a 1 degree C increase in Earth’s temperature?

Global precipitation will only rise about 1-3% per degree C because the atmosphere must radiate away the latent heat released by rain

What is the result of the warming climate and the increase in water vapor illustrated by the Clausius Clapeyron?

There is more water per storm and there are longer dry spells in between storms

Is water vapor actually increasing as a similar rate to the Clausius Clapeyron rate?

Yes, data suggests that the rate of the Clausius Clapeyron is reflective of the increase in the amount of water vapor in the atmosphere.

Do extreme weather events respond more dramatically to climate warming than average conditions do?

Yes. For example in the northeast there has been a 60% increase in the heaviest of 1% of rain days from 1958-2021. The ‘100-year storms’ are getting more common than every 100 years.

What is happening with atmospheric rivers and hurricanes as the amount of water vapor in the atmosphere increases?

Atmospheric rivers and hurricanes are carrying more moisture and produce more rain in a warmer world

What is the equation for runoff?

Runoff = P - ET

If P does not keep pace, what happens to runoff and soil moisture? Runoff = P - ET

If P begins to decline than ET continues to use the same amount of fallen P and runoff decreases. Soil Moisture also decreases as P decreases

What has happened to the Colorado river as the basins have warmed?

The flow of the river has declined. Lake mead and lake powell have hit record lows (dM/dt < 0 is negative so more is flowing out than coming in)

How is the snow line rising as the Earth warms?

The snow line is rising 150m per degree C. There is more rain and less snow, earlier melt, lower summer flow, and rain-on-snow floods

Why is sea-level rising? How much is it rising per year?

sea-level is rising 3-4 mm/yr due to thermal expansion (matter increases volume/size as temperature increases, and land-ice is melting

What is happening to salty and fresh portions of the ocean?

Salty portions of the ocean are getting saltier while fresher regions are getting fresher.

Do humans modify the water cycle directly?

Yes. Humans withdrawal water mostly in agrilculture making up about 70% of withdrawals of the water cycle. Dams lengthen residence time, irrigation cools the surface due to ET storing energy, deforestation, and cities (more runoff)