Climate Variability and Change: Introduction to Course

Climate Variability and Change: Introduction to Course Observed long-term trends: manmade or natural?

Climate Variability and Change: Introduction to Course The coupled climate system has important natural variability

Climate Variability and Change: Introduction Temperature anomalies for July 2010

Climate Variability and Change: Introduction

Climate Variability and Change: Introduction

Climate Variability and Change: Introduction

Climate Variability and Change: Introduction What are the causes of the observed anomalies?

Climate Variability and Change: Introduction Can we predict these anomalies a season ahead?

Climate Variability and Change: Introduction Was the hot July in Western Europe part of a global warming signal?

Climate Variability and Change: Introduction Was the hot July in Western Europe part of a global warming signal caused by us?

Climate Variability and Change: Introduction The global average temperature for July 2013 was 0.61 o C above the 20 th Century average. Is this a global warming signal?

Global Highlights The combined average temperature over global land and ocean surfaces for July 2013 was the sixth highest on record, at 0.61°C (1.10°F) above the 20 th century average of 15.8°C (60.4°F). The global land surface temperature was 0.78°C (1.40°F) above the 20 th century average of 14.3°C (57.8°F), marking the eighth warmest July on record. For the ocean, the July global sea surface temperature was 0.54°C (0.97°F) above the 20 th century average of 16.4°C (61.5°F), the fifth warmest July on record. The combined global land and ocean average surface temperature for the January–July period (year-to-date) was 0.59°C (1.06°F) above the 20 th century average of 13.8°C (56.9°F), tying with 2003 as the sixth warmest such period on record. Climate Variability and Change: Introduction

Climate Variability and Change: Introduction

July 2013 was a warm one in the Northeast. Eleven of the twelve Northeast states ranked this July among their top 20 warmest with Rhode Island and Massachusetts having their warmest July on record. Twenty-six of the thirty-five first order sites ranked this July among their top 20 warmest, with three sites setting monthly temperature records. Climate Variability and Change: Introduction

Climate Variability and Change Affects Society Climate impacts: food and water health infrastructure and transport demography energy

The Sahel (15-20N)

The Sahel experienced one of the most dramatic decadal signals last century

Climate Variability and Change Affects Society in the US Climate impacts: food and water health infrastructure and transport demography energy

Flooding in New Orleans due to Katrina (courtesy NOAA) Bonnie (05) Charlie (05) Frances (05) Ivan (05) courtesy A. Aiyyer Climate Variability and Change Affects Society in the US

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).

Multidecadal 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.

What is the difference between weather and climate? "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."