Climate Variability and Change: Introduction Image from NASA’s Terra satellite Temperature anomalies for July 2010

Climate Variability and Change: Introduction Image from NASA’s Terra satellite Temperature anomalies for July 2010 Eastern Europe: 5C warmer than climatology – severe wildfires and smoke

Climate Variability and Change: Introduction Image from NASA’s Terra satellite Temperature anomalies for July 2010 Eastern Europe: 5C warmer than climatology – severe wildfires and smoke Eastern US: unusual heat

Climate Variability and Change: Introduction Image from NASA’s Terra satellite Temperature anomalies for July 2010 Eastern Europe: 5C warmer than climatology – severe wildfires and smoke Eastern US: unusual heat Parts of S. America: sub- freezing temperatures and heavy snow – hundreds of cold-related deaths

Climate Variability and Change: Introduction Image from NASA’s Terra satellite What are the causes of the observed anomalies?

Climate Variability and Change: Introduction Image from NASA’s Terra satellite Can we predict these anomalies a season ahead?

Climate Variability and Change: Introduction Image from NASA’s Terra satellite Is the hot summer in Eastern Europe part of a global warming signal?

Climate Variability and Change: Introduction Image from NASA’s Terra satellite Is the hot summer in Eastern Europe part of a global warming signal caused by us?

Climate Variability and Change: Introduction Image from NASA’s Terra satellite The global average temperature for July 2010 was 0.55C warmer than climatology (51-80). Is this a global warming signal?

Global Highlights * The average combined global land and ocean surface temperature for July 2012 was 0.62°C (1.12°F) above the 20th century average of 15.8°C (60.4°F). This is the fourth warmest July since records began in * The globally-averaged land surface temperature for July 2012 was the third warmest July on record, at 0.92°C (1.66°F) above average. * The Northern Hemisphere land surface temperature for July 2012 was the all-time warmest July on record, at 1.19°C (2.14°F) above average. * ENSO-neutral conditions continued in the eastern equatorial Pacific Ocean during July 2012 as sea surface temperature anomalies in that region continued to rise. The average July worldwide ocean surface temperature ranked as the seventh warmest July on record. * The combined global land and ocean average surface temperature for January–July 2012 was the 10th warmest such period on record, at 0.53°C (0.95°F) above the 20th century average.

NEW YORK July 2012: tied for 7th warmest July on record Top 10 July temperature anomalies 1st July °F 2nd July °F 3rd July °F 4th July °F 5th July °F July °F 7th July °F July °F July °F July °F

Climate Variability and Change: Introduction Floods in Pakistan (2010) Floods caused by torrential monsoon rains More than 1,600 people died and about 6Million were homeless - about 17 million people were affected

Climate Variability and Change: Introduction Floods in Niger, West Africa (2010, 2012) Heavy rains in August 2010 resulted in floods and left more than 100,000 people homeless (UN).

The Sahel (15-20N)

Climate and its variability impacts society (e.g. food and water resources, health, energy and demography)

Climate Variability Matters!

Climate Variability matters! Flooding in New Orleans due to Katrina (courtesy NOAA) Bonnie (05) Charlie (05) Frances (05) Ivan (05) courtesy A. Aiyyer

Society demands useful predictions of climate so that it can respond to climate variability. One key question to ask is: What do the users of these forecasts need? In recent years most seasonal predictions have been concerned with providing the mean seasonal rainfall anomaly – not always useful. Users tend to want more than this – when will the rainy season start? How will the rainfall be distributed within the season (weather?)? These are much harder to predict. Science and Society Interact

Limits of predictability weather – theoretically 1-2 weeks – TOPS!; currently much less than this, probably around 5 days or so – limitations include poor models and poor observations of the atmosphere especially climate – forecasts are made at seasonal-to-interannual and multi-decadal timescales (including climate change) – limitations include poor models, poor observations of “climate system” – includes land and ocean, less important for weather.

Seasonal-to-Interannual variability We will discuss the basis for these forecasts in this course. Need to understand causes of seaonal-to-interannual variability. At these timescales it is crucial to provide information on the status of ENSO and to be able to predict the impacts of ENSO locally and around the globe (teleconnections).

Interdecadal Fluctuations and Trends Efforts are also made to make predictions on longer timescales

Introduction to the course

Section 1: Introduction to the Climate System Provides background to the mean climate system, combines observations of key variables of the climate system and a physical understanding of key processes. These sections are required for a basic understanding of the climate system and processes before we can attempt to consider its variability. Many textbooks exist that cover these areas.

Section 2 Natural Climate Variability We will consider the nature of observed seasonal-to-interannual variability – (things we wish to predict) - Most importantly in this section is ENSO (observations, mechanisms and impacts (teleconnections). In addition we will discuss decadal variability – important to be aware of this when attempting to attribute anomalies to a “global warming” trend. We will discuss how climate predictions are made Finally we will consider how climate variability is manifested in changes in high impact weather.

Section 3 Climate Change We will consider the theory of climate change We will look at the observational evidence as well as how climate predictions are consistent (or not) with this. The IPCC process will be discussed

Section 4 Future Perspectives We will finish with some discussion on how science and society are interacting with regards to climate variability and change.

"climate is what you expect and weather is what you get." "climate tells you what clothes to buy, but weather tells you what clothes to wear."